Powerful winter storm hits eastern half of the US

Blizzard conditions, severe thunderstorms, damaging winds, heavy rain and bitter cold is lashing parts of the eastern US, as more than 70 million people are under winter weather alerts Friday.

The massive storm is only one piece in a very active weather pattern. Multiple weather hazards were impacting the country Friday morning, and the National Weather Service issued some kind of weather alert for every state.

Everything from blizzard warnings to tornado warnings were in effect early Friday as the massive storm worked its way across the eastern half of the US. Wind alerts stretch nearly 2,000 miles from Texas to New England, while flood alerts span from the mid-Atlantic to Northeast.  

If you’re just reading in now, here’s what you should know:

Nearly 400,000 customers across the country are without power on Friday evening, according to poweroutage.us, which tacks, records and aggregates power outages across the United States.

The Great Lakes area is hit the hardest with more than 234,500 customers without power and Michigan accounts for more than half of that with 127,970 customers in the dark. 

Here’s the region-by-region look of outages as of 9:30 p.m. ET:

Back-to-back storms have hammered the Midwest with heavy snow this week. For Des Moines, Iowa, the one-two punch has resulted the snowiest week since 1942.

The early-week storm brought a foot of snow to the city, while the late-week storm has totaled about nine inches. Combined, Des Moines has seen 21.3 inches of snow since Monday.

Where weather conditions stand now: The snow is tapering off this evening, but wind gusts of 30 to 45 mph will continue tonight and all day Saturday. A blizzard warning is in effect until 6 p.m. Saturday due to continued blowing snow which will create white-out conditions.

Temperatures in Des Moines will remain in the single digits tonight and much of Saturday before dropping below zero Saturday afternoon. Once temperatures drop below zero they will remain there for all of Sunday and Monday — just in time for the 2024 Iowa caucuses, which are expected to be the coldest ever. Wind chills across the state will be as cold as -30 to -45 degrees this weekend into early next week.

Ahead of the incoming severe winter weather, Arkansas Gov. Sarah Huckabee Sanders declared a state of emergency.

Sanders also activated the state’s National Guard to assist with any weather operations alongside state police, according to a news release from the governor’s office.

What to expect from the forecast: Bitter cold sweeping through the middle of the country will impact Arkansas by Sunday through the middle of next week.

Temperatures will struggle to make it past the teens and low 20s for afternoon highs. For most of the state, wind chills will be below zero and in northern parts of the state as cold as negative 20 degrees Fahrenheit.

Snow is expected to impact the state beginning late Sunday afternoon and lasting through Monday. Widespread amounts of four to six inches are expected, with isolated amounts closer to 10 inches possible.

Former President Donald Trump’s campaign on Friday canceled three out of the four in-person campaign events he was scheduled to hold just days before the Iowa caucuses due to extreme weather in the state.

Trump canceled both rallies scheduled for Saturday in Sioux City and Atlantic, and is now holding a tele-rally featuring Iowa Attorney General Brenna Bird in the evening. 

As of now, Trump is still scheduled to hold one in-person rally on Sunday in Indianola. His campaign canceled the second rally he was slated to hold in Cherokee and will instead hold a tele-rally with Iowa State Rep. Bobby Kaufmann. 

Other candidates have also had to cancel campaign events leading up to the caucuses because of extreme weather in the state.

The National Weather Service in Des Moines is warning of “treacherous driving” conditions as well as possible “white-out conditions” as winds become stronger.

“Travel is highly discouraged!” the weather agency said Friday on X.

Winter storms are bringing severe weather to several parts of the US this weekend — including the kind of brutal cold that can cause frostbite.

Frostbite happens when the skin and the tissue under the skin freezes, which can happen much more quickly than you might imagine. It can cause blood clots, gangrene, and long-lasting damage to muscles, tendons, nerves and bones.

The cause: Frostbite is affected by both the outside temperature and the wind chill factor. As the speed of the wind increases, our bodies cool at a faster rate, causing the skin temperature to drop. Higher altitudes can also increase the speed at which skin can freeze.

The National Weather Service has created a wind chill chart that shows the time it might take to develop frostbite at varying temperatures and wind speed. It shows that your skin would freeze in a scant five minutes if you were out in minus 25 degrees Fahrenheit (minus 31.7 degrees Celsius) with a wind speed of just over 25 miles per hour.

Risk factors: You are more susceptible to frostbite if you smoke, take medications called beta-blockers, have poor blood supply to the legs, or have diabetes or Raynaud syndrome, a condition in which strong emotions or cold temperatures cause blood vessels to spasm and block blood flow to extremities.

Older people and people who live outside without proper clothing, heating and food are also at high risk, as are hikers and hunters who aren’t properly clothed and stay outdoors too long.

Here’s more on how to avoid frostbite.

There are now more than 2,000 flight cancellations in the US, according to FlightAware data.

Last year, there were only three days when more than 2,000 flights were canceled, FlightAware data show, making today the fourth worst day for flight cancellations in the last 12 months. It is the most flights cancelled since une 2023.

The vast majority of the cancellations are weather-related, though the grounding of the Boeing 737 Max 9 aircraft after a piece of one plane flew off mid-flight is also contributing to the disruptions.

Chicago is the hardest-hit area, with O’Hare and Midway airports leading the way with cancellations. 

Southwest has the most cancellations – more than 400, or 10% of its flights, according to FlightAware. It does not fly the 737 Max 9 and thus is not impacted by the FAA-mandated grounding. 

In addition to the cancellations, 4,700 flights have been delayed, FlightAware data show. 

The mayor of Buffalo, New York, says the area is prepared for this weekend’s winter weather — and they’re not expecting the type of storm the city dealt with in late 2022, when dozens died.

The forecast: The National Weather Service issued a winter storm warning for Buffalo and the surrounding area from 10 a.m. ET Saturday through to 3 p.m. ET Sunday.

The NWS said heavy lake-effect snow and very strong winds are expected. Blizzard conditions will be possible at times, especially late Saturday night and Sunday morning, according to the winter storm warning.

Preparations: Following the deadly 2022 storm, city leaders faced tough questions about their handling of storm preparations and the disaster response. Mayor Byron Brown said Buffalo is prepared for this new system. Its snow plan will be in full effect, and the city’s emergency manager has met with different city departments.

Illinois Gov. J.B. Pritzker urged Texas Gov. Greg Abbott to stop dropping off migrants from the southern border during the intense ongoing winter storm.

“While action is pending at the federal level, I plead with you for mercy for the thousands of people who are powerless to speak for themselves,” Pritzker wrote. “Please, while winter is threatening vulnerable people’s lives, suspend your transports and do not send more people to our state.”

Pritzker warned that sending migrants to Chicago this weekend could potentially cost lives.

“Your callousness, sending buses and planes full of migrants in this weather, is now life-threatening to every one of the arrivals,” he said in the letter. “Hundreds of children’s and families’ health and survival are at risk due to your actions.”

CNN has reached out to Abbott’s office for comment.  

Maine officials say an iconic state landmark dating back to the 19th century suffered significant damage after it was struck by high waves and winds during the powerful storm sweeping across the eastern half of the United States.

Only one wall of the Pemaquid Point Lighthouse Park bell house, built in 1897, is still standing after 79 mph winds struck it Wednesday, according to Bristol Parks and Recreation Department director Shelley Gallagher.

Gallagher said that — with another powerful storm on the horizon — time is essential to ensure more harm isn’t done to the building. Officials have taken steps to shore up what remains of the structure, but are “very concerned” it isn’t enough, Gallagher said.

The bell house was built to store a 1,000-pound bell that alerted sailors when fog set in and they couldn’t see the lighthouse, according to Gallagher.

Luckily, the bell was not damaged in the storm — it was moved at the end of August because the beam on which it hung was rotting.

“The wall the bell was hanging on isn’t there anymore, and a part of history would have been lost,” Gallagher said.

Heavy snow and blizzard conditions will continue to blast portions of the Midwest. Strong winds will also ramp up across the region, reaching their peak once the powerful storm hits its full strength Friday evening.  

Thunderstorms will continue to roll across the Southeast, where some may become severe through Friday afternoon and evening. Rain and thunderstorms will arrive in parts of the mid-Atlantic by Friday evening and much of the Northeast will deal with rain and potential flooding by Friday night.  

Here’s what a few cities in the path of the storm can expect: 

Chicago: A mix of rain and snow Friday afternoon will gradually turn fully back over to snow Friday evening. Winds will remain gusty throughout the day, with gusts of 40 to 60 mph likely once again Friday night. Snow continues through Saturday as much colder conditions arrive.  

Atlanta: Thunderstorms will continue to develop and move across the city Friday afternoon. Some may become severe, with the potential for damaging wind gusts, hail and even a tornado. A Level 2 out of 5 risk for severe thunderstorms is in place Friday with the potential for damaging wind gusts, hail and even a tornado. Storms will exit the area Friday evening, but breezy conditions will linger through Saturday. 

Washington, DC: Rain and a few thunderstorms will arrive Friday evening and 1 to 2 inches of rain may drench some areas caught under heavy downpours. Winds will be quite strong with gusts of 30 to 50 mph possible. The combination of wind and rain may lead to power outages. Rain will taper off by early Saturday morning, but strong winds will persist. 

New York City: Rain, heavy at times, and strong wind gusts of 40 to 60 mph will arrive Friday night. Rainfall amounts of 1 to 2 inches are likely across the city, with higher amounts possible just north. Rain will taper off Saturday morning, but gusty winds will persist through the weekend.

Widespread wind gusts of 40 to 60 mph are likely across much of the Midwest and portions of the East as a powerful storm reaches its full strength Friday evening. Other portions of the central US will also get quite breezy Friday, with gusts of 30 to 40 mph possible.  

More than 150 million people across the US are under wind alerts as roaring winds crank up in intensity. Multiple locations in northern Illinois — including the Chicago metro area — reported wind gusts exceeding 50 mph Friday morning.

Power outages also started to increase Friday morning, with Illinois and Wisconsin accounting for more than 100,000 outages.

What’s driving the winds: Severe storms aren’t driving these strong, prolonged winds — it’s the impressive strength of the storm, which is an area of low pressure, and how it interacts with a strong area of high pressure located off the northeastern coast of the US. 

The atmosphere is exerting pressure on all of us. The force of that pressure is lower under areas of low pressure and higher under areas of high pressure, hence the names. 

As the storm gets stronger, its pressure drops and it creates a stronger gap in pressure between it and the high pressure, known as a pressure gradient. 

The speed of the wind is related directly to the strength of the pressure gradient, because it squeezes the air that moves through it, forcing it to pick up speed. Think of it like popping bubble wrap: Once it’s squeezed hard enough, the plastic pops and the air quickly rushes out. 

The strength, duration and widespread nature of winds Friday in this pressure gradient are likely to bring down trees and cause additional power outages. 

The number of flight delays and cancellations is ticking up as the Midwest and South are experiencing messy conditions due to the storm.

According to the flight-tracking website FlightAware.com, there have been over 2,400 delays and 1,850 cancellations in the US today so far.

It’s the highest number since July 2023, according to the data from FlightAware.

Chicago-area airports are leading that list, with O’Hare International Airport canceling almost 40% of its flights out and 36% of its inbound flights, and Chicago Midway International Airport canceling about 60% of both outbound and inbound flights.

Other affected airports include Denver International and Milwaukee Mitchell International.

Max factor: Cancellations due to the grounding of the 737 Max 9 planes are also contributing to the totals. More than 200 United and Alaska Airlines flights have been canceled each day this week due to the Federal Aviation Administration-mandated grounding. The FAA and Boeing are still trying to settle on an inspection protocol that would allow those planes to resume flying. 

Most of the cancellations, however, are due to the winter storm. FlightAware shows Southwest, which doesn’t fly the 737 Max 9, canceling nearly 400 flights — the most of any airline.

CNN’s Ross Levitt and Pete Muntean contributed reporting to this post.

Power outages are climbing as the storm unleashes severe thunderstorms in the South, blizzard conditions in the Midwest and strong wind gusts for the more than 150 million Americans under wind alerts Friday.

Nearly 250,000 homes and businesses are without power in the Great Lakes and South as of Friday morning. Most of the outages are in Illinois, where more than 97,000 are in the dark, and winds have gusted as high as 55 mph at Chicago’s O’Hare International Airport.

Severe thunderstorms racing across the South have produced wind gusts as high as 74 mph in Arkansas. 

Here are the top outages by state as of 10:30 a.m. ET:

Satellite imagery captured at least two flashes of lightning occurring over the Chicago area on Friday morning. What’s strange is, the city was experiencing heavy snow and not rain at the time.

Instead of a typical thunderstorm, what unfolded Friday morning was something called thundersnow. 

Thundersnow is exactly what the name suggests – a snowy thunderstorm. It’s a rare phenomenon that occurs in incredibly strong winter storms and sometimes during intense lake-effect snow.  

Typical thunderstorms are fueled by atmospheric instability, which develops from moisture and heat in the atmosphere. As such, lightning is much more common during warmer parts of the year or in warmer locations.  

But lightning isn’t impossible during cold months since very powerful storms like Friday’s can generate plenty of atmospheric instability. A snowstorm can tap into this instability and produce lightning, which is exactly what happened over Chicago.

A snowstorm can tap into this instability and produce lightning, which is exactly what happened over Chicago.

The rumbles of thunder during thundersnow are often muffled by heavy snow. Despite this, lightning strikes during thundersnow are just as dangerous as a typical thunderstorm. 

As a powerful storm moves east across the US and continues to become stronger, it is enveloping more of the Midwest with snow.

Here are the top snowfall reports as of 10 a.m. ET:

Totals in these states will likely climb as snow continues to fall.

The storm has also been accompanied by powerful winds.

Here are the strongest wind gusts from thunderstorms so far:

And the strongest non-thunderstorm wind gusts:

The massive storm slamming the eastern half of the US is only one piece in a very active weather pattern. Multiple weather hazards are impacting the country Friday morning, so the National Weather Service has issued some kind of weather alert for every state.

Everything from blizzard warnings to tornado warnings are in effect early Friday as the massive storm works its way across the eastern half of the US. Wind alerts stretch nearly 2,000 miles from Texas to New England, while flood alerts span from the mid-Atlantic to Northeast.  

Another robust storm in the Northwest is bringing snow and wind to the region and temperature alerts dot several states as brutally cold air starts to seep south out of Canada. 

Alerts are in effect in Alaska ahead of a winter storm set to impact the state this weekend. Even Hawaii is dealing with the impacts of stormy weather as a potent cold front slices across the islands.

Track winter weather alerts across the US here.

The potent storm tracking across the central US will continue to strengthen on Friday, bringing all modes of hazardous weather to the eastern half of the country.  

At the storm’s peak intensity Friday night, it may strengthen enough to bomb out, or be considered a bomb cyclone: a rapidly strengthening storm that undergoes a significant drop in pressure — a measure of a storm’s strength — in a short time. Bomb cyclones are formidable and unload heavy snow and strong winds during the winter. 

A storm must drop at least 24 millibars (which is a unit of pressure) in 24 hours or less to meet bomb cyclone criteria. But technically, the exact millibar drop needed will vary slightly based on the storm’s exact latitude.  

The Weather Prediction Center doesn’t show the storm officially hitting bomb cyclone status, but several forecast models showed the potential exists. Bomb cyclone or not, it could end up stronger than the last powerful storm, which set January records for strength as it passed over Indiana.

Water levels on Maine’s coast are forecast to hit historic highs on Saturday, threatening to inflict more damage on coastal communities still reeling after a storm earlier this week sent water surging onshore.

Water levels at gauges from Portland to Eastport were forecast to top levels from Wednesday during the last storm, according to data from the National Oceanic and Atmospheric Administration. Portland and Bar Harbor both hit new historic high-water marks on Wednesday.

The water level reached 15.49 feet in Bar Harbor Wednesday morning and is forecast to top 17 feet by noon Saturday. The previous record in Bar Harbor was 15.04 feet in 2018.

The water is projected to top 14 feet in Portland Saturday morning, slightly higher than the 13.84 feet hit on Wednesday morning, which broke the previous record set in 1978, NOAA said. 

Maine’s governor issued a State of Civil Emergency Thursday for all eight of the state’s coastal counties after the storm surge caused destruction there.

“Significant rain, wind, and flooding have once again ravaged our state – this time our small communities up and down the coast,” Gov. Janet Mills announced Thursday. “The damage we are seeing is devastating, from working waterfronts, to small businesses, to public roadways and more.”

The exceptionally high water is being driven by strong winds blowing water from the Atlantic Ocean toward the shore on top of high tide. Heavy rain inland only exacerbates the flooding. 

Climate change is also playing a role. Sea levels are rising as global temperatures climb and melt glaciers and ice sheets. Higher sea levels are making coastal flooding events worse and will continue to do so in the future. 

Heavy, wet snow is moving across the Chicago area early Friday morning and could leave some parts of the metropolitan area with close to 6 inches of snow by the afternoon.

The National Weather Service in Chicago urged people across northern Illinois to “strongly consider postponing travel” Friday morning, warning of snowfall rates of 1 to 2 inches per hour.

The most snow will be largely in the western and northern Chicago suburbs Friday morning, away from the influence of Lake Michigan’s abnormal warmth.

Snow will mix with rain across southern portions of the metro and areas along the lakeshore Friday afternoon, before changing back over fully to snow Friday evening once colder air arrives. Steady snowfall throughout the day will send totals skyrocketing for areas away from the lakeshore.

Very strong winds will arrive Friday evening across northern Illinois and combine with falling snow for another period of treacherous travel across the region, Chicago included.

More than 5 million people across portions of Texas, Arkansas, Louisiana, Tennessee and Mississippi are under a tornado watch as intense thunderstorms rumble across the South Friday morning.

The tornado watch is in effect until 11 a.m. CT and includes Little Rock, Arkansas, Shreveport, Louisiana, and Jackson, Mississippi.

Thunderstorms stretch from the Texas Gulf Coast as far north as Illinois and Indiana early Friday morning.

But the greatest risk for these storms to turn severe and unload damaging winds, hail and tornadoes is over the Lower Mississippi Valley, where a Level 3 out of 5 risk for severe thunderstorms is in place.

Another bout of rain will fall on the already-soaked Northeast on Friday, threatening to trigger disruptive and damaging coastal flooding in several of the region’s major cities through Saturday.

More than 7 million people are under coastal flood warnings along swaths of the Northeast, including residents of Philadelphia and parts of New York, where Nassau and Suffolk Counties could be overwhelmed with up to 3 feet of coastline flooding.

“This will result in extensive road closures and flooding of low-lying property including parking lots, parks, lawns and first floors and basements of homes/businesses near the waterfront,” the National Weather Service in New York warned. “Vehicles parked in vulnerable areas near the waterfront will likely become flooded and/or submerged.”

In New York City, where a coastal advisory is in place, 1 to 2 feet of water could inundate ground-level areas. 

About 35 million people – stretching from North Carolina to eastern Massachusetts – are under flood watches Friday as the storm pushes through the eastern US.

More than 50 million people are under a severe storm threat across the Southeast on Friday after overnight storms brought high winds and almost a dozen reports of large hail in the South.

Parts of northern Alabama and Mississippi are the most at-risk for severe weather, with the main threats being powerful winds, large hail and a chance of tornadoes.

A tornado watch is in effect until 5 a.m. ET for parts of western and central Arkansas, northwestern Louisiana, southeastern Oklahoma and northeast Texas.

Other major cities in the storm’s path include New Orleans, Atlanta, Nashville, Tennessee, and Tampa, Florida. 

As winter weather sweeps the country, more than 1,170 flights have been canceled within, into or out of the United States so far today, according to tracker Flight Aware.

In Chicago, which is set to receive more than 8 inches of snow, O’Hare International Airport tops the charts with more than 400 flights canceled in and out of the travel hub. The city’s other airport, Midway International, is also among the hardest-hit with more than 100 cancelations.

Other airports with a high number of cancelations include Denver International Airport in Colorado, Milwaukee Mitchell International Airport in Wisconsin and Newark Liberty International in New Jersey.

Here’s what to do if your flight is canceled or delayed.

Here’s a look at the snowfall and other conditions expected in some of the Midwestern cities in the storm’s path. All times are local to the cities indicated.

Chicago

Des Moines

Grand Rapids

Milwaukee

Minneapolis

A powerful storm is set to unleash blizzard conditions, severe thunderstorms, damaging winds and brutal cold across the eastern half of the US in what will be a dangerous dose of déjà vu for many.

When staying indoors during cold temperatures or a winter storm, the US Centers for Disease Control and Prevention offers these tips:

And if you must go outside, the CDC and National Weather Service have some recommendations for staying safe while venturing outdoors during a winter storm,

Read more about how to stay safe during winter weather.

Iowa is one of the states where blizzard conditions are expected Friday – and blizzard warnings will soon cover a majority of the Hawkeye State.

Pelting snow and winds are expected to create whiteout conditions and heavy snow accumulations. Widespread snowfall totals of 6 to 11 inches are expected in the state.

The warnings are set to be in place from 10 a.m. Friday to 6 a.m. Saturday CT and include the cities of Des Moines, Davenport, Waterloo, Ames, Sioux City and Cedar Rapids.

“Storms of this magnitude are fairly rare with recurrence around once or twice per decade,” the National Weather Service in Des Moines said. “Travel is not recommended except if absolutely necessary, especially by Friday afternoon into the evening.”

Severe thunderstorms that may produce dangerous tornadoes will threaten parts of the South overnight and into the daylight hours Friday morning.

Nighttime tornadoes are twice as likely to be deadly as those that occur during the day, a 2022 study found.

Researchers found that nighttime tornadoes from 1950 to 2019 made up less than a third of tornadoes, but were responsible for a staggering 42% of tornado deaths.

Tornado fatalities during the daytime hours have decreased by 20% since the late 1800s because of advances in science and communication, the study found. But the amount of nighttime tornado fatalities actually increased by 20% during the same period.

The increase could be due to factors like location and home construction, but the researchers said the most obvious issue is a large portion of the population is asleep at night and may miss life-saving warnings.

It’s difficult to spot a tornado at night, even for those who are awake or are awoken by warnings.

The best way to stay safe during a nocturnal tornado threat is to have multiple ways to receive severe weather warnings. At the very least, make sure emergency alerts are enabled on your smartphone. Charge devices ahead of time and set phones or alarms on a loud volume so you’re not caught unaware.

Significant snow is on the way for the greater Chicago area, but totals will vary wildly from an inch or two to closer to double-digits depending on where you are. 

“We are expecting a tight gradient in snow across a few miles inland from Lake Michigan,” Brett Borchardt, a meteorologist with the National Weather Service in Chicago, told CNN.  

Meaning parts of Chicago close to the lakeshore are likely going to end up with significantly lower snowfall totals than those in the western suburbs Friday through Saturday.  

This difference is tied back to the warmth of Lake Michigan, according to Borchardt. 

Water temperatures on the surface of Lake Michigan are currently higher than they’ve been since records began in 1995, according to data from NOAA. Because of this warmth, the total percentage of the lake covered in ice is hovering near-zero. At this point in January, at least 10% to 20% of Lake Michigan should be covered in ice.  

With warm waters and almost no ice, air temperatures near the lakeshore become warmer than typical. When air temperatures hover at or just above freezing, snow is unable to accumulate easily, lowering totals.  

Snow will accumulate more readily in areas farther from Lake Michigan where air temperatures are able to drop below freezing.  

“It’s best to prepare for difficult travel conditions regardless of how much snow falls, especially Friday night as winds pick up and lead to areas of blowing snow including in Chicago,” Borchardt cautioned.  

While the northern side of the storm will deliver snowy and windy conditions, severe thunderstorms are possible Friday on the southern side – including for a significant portion of the South and portions of the mid-Atlantic.

Early Friday, before sunrise: Parts of Arkansas, eastern Texas and northwestern Louisiana, including Shreveport, have an enhanced risk of severe storms, or a Level 3 of 5, according to the Storm Prediction Center.

A slight risk for severe storms, or Level 2 of 5, exists early Friday for a wider area, from eastern Texas to western Mississippi. The main threats there are tornadoes, strong gusts and large hail.

Friday, during the day: An enhanced risk of severe storms, or a Level 3 of 5, exists for a large portion of northern Mississippi and part of western Alabama, according to the Storm Prediction Center. A slight risk for severe storms, of Level 2 of 5, exists for a wider portion of the Southeast from the rest of Mississippi to much of the Carolinas, including the areas of Birmingham, Alabama; Memphis, Tennessee; and Charlotte and Raleigh, North Carolina.

Snow will once again bury portions of the Midwest as a powerful storm tracks through the region Friday and Saturday.

The combination of heavy snow and strong winds could make travel dangerous and even impossible in some areas, especially late Friday through Friday night. 

Whiteout conditions are possible from Iowa to Michigan, and people may even find themselves stuck in a blizzard.  

Snowstorms are not considered blizzards until they meet certain criteria.  

Blizzards occur when snow and sustained winds of 35 mph or greater combine for at least three hours and reduce visibility to a quarter-mile or less, according to the National Weather Service. More simply: strong winds blow so much snow around that it’s impossible to see a distance farther than a few football fields for a long period of time. 

Visibility can plummet to near-zero, meaning it’s impossible to see farther than a few feet, in the most intense blizzards. 

But remember: A storm doesn’t need to meet the technical definition of a blizzard in order to cause life-threatening conditions.  

Storms with similar wind speeds and snow amounts that happen on short timescales are also very dangerous. Whiteout conditions for any length of time may lead to serious accidents and deadly crashes.