While much of the United States is catching a break from unusually high temperatures, it’s abnormally hot in South Florida and poised to turn even hotter in South Texas.
The record-threatening heat could last through the weekend. Then it’s expected to head westward into Texas.
Parts of South Texas should get a taste of what’s to come on Thursday and Friday with temperatures around 100, but the heat is expected to turn much worse next week and may last awhile.
South Florida under suffocating heat
Much of South Florida, mainly inland of its southeast coast, is under an extreme Level 4 out of 4 threat from heat, according to the National Weather Service’s HeatRisk outlook.
“Today will be the hottest day of the week thus far for most areas, with high temps in the mid-90s and heat index values around 100-105,” the Weather Service office serving the Miami area wrote.
Key West and West Palm Beach are forecast to set records Wednesday, with predicted highs of 92 and 95, respectively. Miami, Vero Beach, Fort Lauderdale and Marathon could also challenge records.
Nighttime low temperatures are likely to be stuck near or above 80 degrees in the far south of the state and into the Florida Keys.
Miami will break its second record-warm low in a row if it holds through Wednesday, according to local meteorologist Brian McNoldy. Key West is set to challenge record-warm lows in the low 80s daily through at least Monday.
The same areas were scalded by relentless extreme heat in 2023. Miami and Key West both had their hottest summer on record, among others.
Heat forecast to spread to Texas and eventually the Southwest
In South Texas, which endured record heat last week (Brownsville posted a heat index of 129 degrees on Thursday), more big waves are coming.
A handful of record highs in the mid-90s to near 100 are possible to close the workweek, as are record-warm lows in the mid-70s to near 80.
“When combined with relative humidity percentages, heat index values will near, or even briefly touch, established Heat Advisory criteria for portions of Deep South Texas and the Rio Grande Valley,” the Weather Service office serving Brownsville and South Texas wrote.
Heat indexes are forecast to rise to a range of 105 to 115 in the area Thursday and again on Friday.
While impressive for mid-May, a more potent influx of heat is still a few days off. Starting this weekend, an intense zone high pressure over Mexico or heat dome is forecast to bulge into the southcentral United States.
Temperatures are expected to climb at least 5 to 10 degrees above normal for an extended period. Record-threatening highs of 105 degrees or higher are forecast in Del Rio, near the border with Texas, starting Saturday and then lasting through Tuesday and probably beyond.
Weather models project that once the furnace comes on, there’s little sign it will back off through the rest of May.
Abnormally warm oceans and drought feed the heat
Even though the climate pattern El Niño, which heated many parts of the world, is easing, temperatures remain elevated. This is especially true of ocean temperatures.
The Gulf of Mexico and Atlantic Ocean are more than 2 degrees above average and somewhat warmer than the same time last year.
A developing La Niña climate pattern tends to favor hot and dry conditions in the southern and central United States as well as Mexico. This idea is supported by a hot and dry summer outlook from the National Weather Service.
Meanwhile, severe to exceptional drought in Mexico is contributing to record heat on nearly a daily basis there. The hot air in Mexico tends to intensify the heat domes that then migrate northward over the southern United States.
In addition to contributions from El Niño, La Niña and drought, human-caused climate change is boosting the intensity and longevity of extreme heat. Climate Central’s Climate Shift Index indicates that Wednesday’s extreme heat in South Florida was made three times more probable by human-caused climate change.
Jason Samenow contributed to this report.
