Chicago's allergy seasons are starting earlier and lasting longer

While there are so many things to look forward to with the arrival of spring in Chicago, there are few things I dread. I have already had my first tick bite. Now I am waiting for the sniffles, scratchy throat and itchy, watery eyes that come with the start of allergy season.

Climate change is lengthening allergy season and making allergies worse. An expansive study by Climate Central confirms it. They analyzed temperature data for more than 200 cities in our country and shared their results in a recent report.

They looked at over 50 years of temperature data and found the vast majority (85%) of cities have seen their freeze-free seasons get longer since 1970. The average extension of the freeze-free season has stretched by more than two weeks (15 days). More than 30 cities saw it lengthen by at least a month. The Central region saw the freeze-free season lengthen by just under two weeks (13 days).


According to UChicago Medicine our trees in Chicago typically pollinate in the spring months of March, April and May. Grass pollinates a little later, in the months of May and June. Finally, weeds pollinate from the middle of August through the final days of September.

Here are some of the conclusions from the Climate Central report:

  • The first leaves and blooms of spring are arriving days to weeks early in parts of the U.S., according to the USA National Phenology Network (USA-NPN). Some areas in the East and South are seeing the earliest spring on record. 
  • This is bad news for people with seasonal allergies—about one-quarter of adults (26%) and 19% of children in the U.S., according to the Centers for Disease Control and Prevention.
  • Earlier spring and longer periods of freeze-free days mean that plants have more time to flower and release allergy-inducing pollen. A recent study found that North American pollen seasons became longer (by 20 days on average) and more intense (21% increase in concentrations) from 1990 to 2018.
  • 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

Climate Central’s report, Seasonal Allergies: Pollen and Mold, has more details on how climate change means allergy season is starting earlier, lasting longer and having worse health impacts.

Chicago's allergy season has grown considerably longer since 1970. Climate Central's study shows it has expanded by fourteen days. 

Nearly a quarter of our country's adults and a fifth of its children have seasonal allergies according to the Centers for Disease Control and Prevention. Plant pollen usually peaks in either spring, summer or fall depending on the type of pollen and the location. Some molds can also be allergenic. The tiny spores that molds may release are usually most abundant in late summer and fall. That means people who suffer from both types of allergies can be impacted through most of the year in some cases.

Here are some helpful links for those of us who suffer from seasonal allergies: