Mar. 22—For how pretty her city of Philadelphia has been this month with pink cherry blossoms and dogwoods blooming early, Lauren Casey knows those flowers also represent a problem.

The trees are blooming prematurely because the winter has been so mild, are more proof that freeze-free periods have grown longer in many parts of the country, including most of southeast Pennsylvania, she said.

As a result, pollen is spreading over a more extended time, making allergy season longer and worse, she said.

Itchy eyes, sneezing, coughing, and stuffy noses have already begun for many.

"Spring this year started weeks earlier. It's crazy," said Casey, a meteorologist with the Climate Center, a nonprofit news organization that analyzes and reports on climate science.

The group has found that in Philadelphia, the freeze-free season is 32 days longer now than it was in the 1970s. That is playing a crucial role in how much pollen is produced, distributed, and in the air at any given time.

Plants are leafing and blooming earlier, and the overall growing season is lasting longer across much of the U.S., the center's recent report shows. Analysis of temperature data for 203 American cities shows the freeze-free season extended by more than 15 days on average since 1970, with 85 percent of those cities seeing their freeze-free seasons lengthen.

For many of the approximately 50 million Americans that suffer from seasonal allergies to pollen and mold, their symptoms and health risks are already activated this year, according to a report by AccuWeather.

The National Weather Service said that includes southeast Pennsylvania, where both January and February were warmer than usual, spurring those early blooms.

As a result, several Berks County doctors said they've already treated numerous patients who complained of early allergy symptoms.

"I've been seeing it since mid-February," said Dr. Madushini Craner, a family medicine physician with Tower Health Medical Group. Within the last few weeks she treated about a dozen patients seeking help for their allergy symptoms.

Those prone to allergies should check online pollen reports daily, limit their time outdoors to avoid expose on high pollen count days, and save their gardening for other times, Craner said.

"Know the triggers and take steps to avoid them," she said. "Proper planning can help you avoid exposure."

The USA National Phenology Network, a nonprofit science group that provided much of the data for the Climate Center report, said both historic temperature comparisons and observations of what's blooming show the warming trend and extended allergy season are occurring.

"In some places, this is the earliest spring leaf out and blooms on record," said Samantha Brewer, volunteer engagement coordinator for the Phenology Network.

Seasonal allergies can already last from early spring through late fall, but warming temperatures and shifting seasonal patterns — both linked to climate change and greenhouse gas emissions — are expanding allergy season and its impacts on respiratory health, the Climate Center said.

AccuWeather said trees are commonly the first and most prominent producers of pollen in the spring, while by late spring and early summer grass pollen will start to dominate, and finally, toward the late summer and early fall, weed pollen will take over for the rest of the season.

Berks Community Health has patients who are already suffering from pollen allergies, said Dr. Mary Kelleher, chief medical officer.

Kelleher knows how problematic seasonal allergies can be because her daughter too suffers from them, and is already feeling the affects this year.

"She sometimes feels like she has glass in her eyes," Kelleher said. "Allergies can be miserable."

Those seeking help can try preventive measures such as spending more time indoors and closing windows, or if symptoms persist try over-the-counter allergy medicines. Those with more allergy issues may need to see a specialist and receive allergy shots, she said.

Kelleher said those affected should probably expect the early allergy season to continue in coming years.

"The seasons seem to be changing," she said.