When is allergy season in Chicago? Chicago’s outdoor pollen season generally begins with tree pollen in March, continues with grass pollen in May and June then shifts to weed pollen from mid-August through September. Exact timing and pollen levels can change with the weather.
Chicago may have four official seasons, but your nose knows there are a few extras.
As the city warms up, trees, grasses and weeds take turns releasing pollen. That means allergy season in Chicago is less like one big event and more like a seasonal handoff from spring through fall.
Here’s what may be floating around throughout the year, which months can be trickiest, when Chicago’s pollen season generally winds down and how to build a simple routine for washing off the day — nose included.
When is allergy season in Chicago throughout the year?
Chicago’s main outdoor pollen season generally stretches from March through September, beginning with trees, followed by grasses then weeds.
Weather can change how much pollen is actually in the air on any given day, so think of these months as a general calendar rather than a pollen appointment you can put in your phone.
March through May: Tree pollen kicks things off
Trees are typically first up. In Chicago, tree pollination generally happens throughout March, April and May.
Across Illinois and the Midwest, common pollen-producing trees can include oak, maple, birch and elm. Exactly what you react to depends on your individual sensitivities and what’s growing around you.
The trees are waking up. Your nose noticed.
For a deeper dive into what’s floating around, read our guide to pollen season.
May and June: Grass pollen joins the party
As spring turns into summer, grass takes its turn. UChicago Medicine reports that grass generally pollinates in Chicago during May and June.
Grass species such as ryegrass and Kentucky bluegrass can contribute pollen, and there may be overlap between tree and grass seasons. Nationally, tree pollen tends to dominate earlier in spring while grass becomes more prominent in late spring and early summer.
Translation: picnic season and pollen season have unfortunately compared calendars.
Mid-August through September: Weed pollen makes a comeback
Thought you were in the clear? Not quite.
Chicago’s weeds generally pollinate from mid-August through the end of September. Ragweed is an especially important late-summer and fall allergen across the Midwest.
Other weed pollens may include pigweed and similar late-season plants. Ragweed season can continue until the first hard frost, which means the weather helps determine exactly when the fall pollen party wraps up.
What are the worst months for allergies in Chicago?
There isn’t one single worst month for everyone because different allergens peak at different times.
If tree pollen is your trigger, March through May may be your more noticeable stretch. Grass-sensitive people may have more trouble in May and June, while people sensitive to ragweed and other weeds may notice symptoms beginning around mid-August and continuing through September or until frost.
There can also be overlap between pollen seasons, so your personal “worst month” depends on which plants you’re sensitive to and that year’s weather.
Think less “allergy month,” more personalized pollen calendar.
What can Chicago seasonal allergies feel like?
Seasonal pollen and mold allergies can cause symptoms including sneezing, a stuffy or runny nose, itching and red or watery eyes.
You may also notice itching in the nose, ears, mouth or throat and swelling around the eyes. These symptoms happen when someone who is allergic to a particular airborne allergen is exposed to it.
Symptoms can overlap with other conditions, including non-allergic rhinitis and respiratory infections. If symptoms are severe, persistent, unusual or you’re not sure what’s causing them, talk with a healthcare professional.
Is it allergy season in Chicago right now?
If you’re wondering “is it allergy season in Chicago?”, start with the calendar, then check current local pollen conditions.
Your quick mental map looks like this: trees in spring, grasses in late spring and early summer and weeds in late summer and fall.
But pollen doesn’t follow a perfectly neat schedule. Weather can change the amount that becomes airborne. UChicago Medicine notes that dry, windy conditions tend to increase airborne pollen while rain generally lowers it. Pollen counts also tend to rise toward midday.
Checking a local pollen count alongside your weather app can give you a better idea of what’s actually happening outside today. Pollen counts reflect measured conditions while pollen forecasts are predictions based on factors such as historical pollen data and weather.
If your nose seems bothered regardless of the season, outdoor pollen may not be the whole story. Dust mites, pet allergens, cockroaches and indoor mold can contribute to year-round allergic rhinitis too.
Our guide to indoor allergies breaks down what may be hanging around at home.
Why can Chicago allergy season feel so long?
Chicago allergy season can feel long because different pollen sources peak at different points from spring through fall — and mold can add another seasonal trigger.
Think relay race, not marathon.
Trees take the first leg. Grass grabs the baton in late spring. Then weeds, including ragweed, bring things home in late summer and fall.
Mold spores can add another layer. UChicago Medicine notes that mold allergies can begin around early June and may become more noticeable in damp weather and when leaves decay in fall.
Weather adds another variable. Hot, dry and windy conditions can help pollen travel while rainy, cloudy or windless conditions may temporarily reduce the amount moving through the air.
And pollen can follow you home on clothes and hair. Which brings us to the part you can actually control: your routine.
How can you prepare for allergy season in Chicago?
Knowing when allergy season is in Chicago can help you plan for pollen instead of being personally offended by it every spring.
A few simple habits can help reduce exposure.
Check what’s outside before you go outside
Check local pollen levels before a long lakefront walk, park day or afternoon on a patio.
On high-pollen days, timing can help. UChicago Medicine reports that pollen counts tend to be lowest before dawn, rise toward midday then gradually fall later in the day. It recommends choosing morning rather than afternoon for outdoor activities when pollen counts are high.
Keep a little more pollen outside
Keeping windows closed during high-pollen periods can help limit what comes indoors. Wraparound sunglasses may also reduce exposure around the eyes on high-pollen days.
Appropriate air filtration can be another useful part of reducing environmental exposure, particularly for people who deal with multiple indoor and outdoor allergens.
Wash off the day when you get home
Pollen does not need an invitation to come inside.
Changing your clothes and showering after significant outdoor exposure can help remove pollen you picked up throughout the day. UChicago Medicine specifically recommends showering and changing clothes after returning home on high-pollen days.
Don’t forget your nose
Your nose spends all day interacting with the air around you, so it makes sense to include it in the rinse-off routine too.
Saline nasal rinsing can physically cleanse pollen and other particles from the nasal passages. Sinus Rinse Free + Clear can fit into your post-outdoors routine as a gentle, everyday cleansing step. When you’re looking for a deeper clean, Advanced Sinus Rinse Free + Clear offers a more thorough rinse for mucus and allergens.
Face washed. Hair washed. Nose washed. Consider the day officially rinsed.
How can Wizard fit into your Chicago allergy season routine?
At Wizard Wellness, we think nasal care deserves a spot alongside the everyday wellness rituals you already have down.
After time outside, start with a nasal rinse to cleanse away pollen, dust and other particles you’ve encountered throughout the day. Then add Daily Nasal Spray as a refreshing step in your routine.
Wizard’s approach puts the nasal microbiome at the center of everyday nasal wellness. Our proprietary Nasalbiome™ Technology is designed to support a balanced nasal microbiome — unstuffy science for a very stuffy subject. Learn more in our guide to the nasal microbiome.
Treat it like skincare: cleanse, refresh, get on with your day.
When should you see an allergist?
Consider seeing an allergist if your symptoms are persistent, significantly affecting your day or aren’t improving with the approaches you’re already using.
An allergist can help determine which allergens may be responsible for your symptoms. UChicago Medicine notes that testing may involve skin or blood tests, depending on the individual situation.
Knowing your specific triggers can make it easier to understand your personal allergy calendar and make more targeted choices about reducing exposure.
So, when is Chicago allergy season actually over?
When is allergy season in Chicago officially over? There isn’t one exact date, but the city’s major outdoor pollen season generally winds down in fall after weed and ragweed season.
Knowing the general calendar — trees in spring, grass in late spring and early summer and weeds in late summer and fall — can make it easier to understand what may be in the air and adjust your routine accordingly.
If you’re asking when is allergy season in Illinois, the same broad seasonal pattern applies, though exact timing can differ across the state and shift with weather.
Check current pollen conditions, get to know your individual triggers and make washing off the outdoors part of your routine.
Chicago summers are too short to spend the whole thing side-eyeing every tree.
Frequently asked questions
When is allergy season in Illinois?
Illinois’ outdoor pollen season generally follows the Midwest pattern: trees in spring, grasses in late spring and early summer and weeds in late summer through fall. In Chicago specifically, UChicago Medicine reports tree pollination in March through May, grass in May and June and weeds from mid-August through September.
Is it allergy season in Chicago right now?
It depends on the time of year and your individual triggers. Tree pollen is generally present in spring, grass pollen in late spring and early summer and weed pollen in late summer and fall. Checking current local pollen counts can give you a clearer picture of what’s in the air today.
What are the worst months for allergies in Chicago?
There isn’t one worst month for everyone. March through May is Chicago’s main tree-pollen window, grass generally pollinates during May and June and weeds typically pollinate from mid-August through September. Your personal peak depends on what you’re sensitive to.
When does ragweed season start in Chicago?
Ragweed is part of the late-summer and fall weed pollen season. Chicago weeds generally begin pollinating around mid-August, while ragweed across much of the U.S. typically appears around August and can continue until the first hard frost.
Why are my allergies so bad in Chicago?
Chicago allergies can feel especially noticeable because different allergens peak throughout the year, from tree pollen in spring to grass in early summer and ragweed in late summer and fall. Weather, mold and indoor allergens can also contribute, so your experience depends on your individual triggers.