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*Disclaimer: HeyAllergy® provides all clinical services furnished to patients in California, Florida, Texas, Illinois, Nevada, Pennsylvania. In New York, clinical services are furnished by Hey Allergy Medicine.
Real-time pollen data for Chicago — updated daily. Powered by board-certified allergists.
Tree pollen drives Chicago's first and most intense allergy wave each year. Oak is the dominant tree allergen in the Chicagoland area, producing heavy pollen loads from April through May with a long pollination window. Birch trees are particularly problematic in northern Illinois, releasing highly allergenic pollen from March through April. Maple, elm, ash, hickory, cottonwood, and walnut trees all contribute significantly. Cottonwood produces visible white "fluff" that blankets neighborhoods in late spring — while the fluff itself isn't highly allergenic, it carries other pollen grains with it.
What makes Chicago different: The Lake Michigan "lake effect" creates rising air currents that can spread and disperse pollen more widely across the metro area than in inland cities. Combined with Chicago's famous wind, pollen can travel significant distances from parks and tree-lined neighborhoods to areas with minimal vegetation.
Grass pollen season overlaps with late tree pollen in May, creating a particularly difficult transition period. Timothy grass, Kentucky bluegrass, ryegrass, orchardgrass, fescue, and Bermuda grass are the primary grass allergens in the Chicago area. The city's extensive park system — Lincoln Park, Grant Park, Humboldt Park, Washington Park — and the suburban lawns stretching across Cook, DuPage, and Lake counties are major sources. Grass pollen peaks in June and can remain elevated through mid-July.
Prairie grasses native to Illinois also contribute to the pollen load. The region's agricultural landscape surrounding the metro area adds a rural pollen component that reaches the city on prevailing winds.
Ragweed is Chicago's most significant fall allergen and one of the top allergens in the entire Chicagoland area according to official pollen monitoring stations. Ragweed season begins in August and peaks in early-to-mid September, with pollen counts frequently reaching "High" to "Very High" levels. Chenopods (lamb's quarters), nettle, pigweed, mugwort, and wormwood are additional weed triggers common in vacant lots, roadsides, and disturbed urban land throughout Cook County.
Climate change has been extending Chicago's ragweed season, with warmer falls delaying the first hard frost — historically arriving in mid-to-late October — that kills ragweed plants and ends the outdoor pollen season.
Chicago's harsh winters mean residents spend approximately five months with windows sealed and heating systems running, concentrating indoor allergens. Dust mites thrive in carpeted apartments and homes with forced-air heating. Mold grows in basements and older buildings — particularly relevant in Chicago's large stock of vintage housing. Cockroach allergens are a significant factor in multi-unit buildings across the city, contributing to elevated childhood asthma rates. Pet dander from cats and dogs compounds the problem for the estimated 30% of allergy sufferers who are sensitized.
The transition from outdoor to indoor allergen dominance in November can catch people off guard — symptoms that seem to "never go away" despite the end of pollen season often indicate underlying indoor allergen sensitization.
Chicago's cold winters suppress outdoor pollen almost entirely from December through February, providing genuine relief for pollen-sensitive residents. However, sealed-up homes with forced-air heating concentrate indoor allergens — dust mites, mold, pet dander, and cockroach allergens — making winter a difficult period for those with perennial allergies. By late February or early March, depending on winter severity, elm and maple trees may begin releasing early pollen as the first thaw arrives.
Top allergens: Dust mites, indoor mold, pet dander, cockroach allergens
Severity: Minimal (outdoor), moderate (indoor)
Tip: Chicago's dry winter air tempts people to run humidifiers on high — but keep indoor humidity below 50% to prevent dust mite and mold growth. Change furnace filters monthly during heating season.
This is Chicago's worst allergy period. Oak, birch, maple, ash, hickory, and cottonwood trees release massive pollen loads across the metro area. April typically marks the rapid escalation, with pollen counts jumping from Low to Very High within days of the first sustained warm spell. May brings the overlap of late tree pollen with early grass pollen — a brutal combination for multi-sensitized individuals. Lincoln Park, the lakefront parks, and tree-lined neighborhoods throughout the North Side and suburbs become major allergen sources.
Top allergens: Oak, birch, maple, elm, ash, cottonwood, early grass
Severity: High to very high
Tip: Start your allergy regimen by mid-March, before tree pollen arrives. Track the official Chicago pollen count — the Asthma and Allergy Center of Chicago provides daily readings from April through October.
Grass pollen takes center stage as Timothy grass, bluegrass, ryegrass, and fescue peak in June. By mid-July, grass pollen begins declining, but warm, humid summer conditions drive mold spore counts higher. Chicago's summer thunderstorms temporarily wash pollen from the air but trigger mold surges afterward. Lake Michigan moderates temperatures near the lakefront but the humidity contributes to mold growth across the metro area.
Top allergens: Timothy grass, bluegrass, ryegrass, mold spores
Severity: Moderate to high
Tip: If you attend outdoor festivals like Taste of Chicago, Lollapalooza, or neighborhood street fests, premedicate and shower immediately when you get home. Extended outdoor time during grass pollen season accumulates significant allergen exposure.
Ragweed dominates Chicago's fall allergy season and is one of the top allergens in the metro area. Pollen counts peak in early-to-mid September, often reaching "Very High" levels. Ragweed pollen travels hundreds of miles on the wind, so even residents who don't live near ragweed plants are affected. Mold spore counts also rise as fallen leaves decompose across the city's parks and residential areas. The season ends with the first hard frost, typically in mid-to-late October.
Top allergens: Ragweed, nettle, chenopods, mold spores
Severity: Moderate to high (ragweed can be very high in September)
Tip: September is Chicago's sneakiest allergy month — beautiful fall weather encourages outdoor time right when ragweed peaks. Check counts before heading to the lakefront trail or neighborhood parks.
The first hard frost ends ragweed and outdoor pollen season. November and December are Chicago's lowest-allergen months outdoors. However, the transition to sealed windows and full-time heating reignites indoor allergen issues — dust mites stirred up by forced-air systems, mold in basements, and pet dander concentrated in smaller spaces. Holiday activities can also introduce allergens: natural Christmas trees harbor mold spores, and holiday gatherings in pet-owning homes increase dander exposure.
Top allergens: Indoor mold, dust mites, pet dander
Severity: Minimal (outdoor), low to moderate (indoor)
Tip: Deep clean before sealing up for winter — vacuum with HEPA filters, wash all bedding, and address any basement moisture or visible mold. This sets you up for a healthier winter indoors.
Chicago's position on Lake Michigan creates a unique "lake effect" that influences allergy patterns. Rising air currents from the lake can spread and disperse pollen more widely than in inland cities. Onshore (easterly) breezes can push pollen from lakefront parks deep into neighborhoods, while offshore winds carry pollen from suburban and agricultural areas toward the city. On days with strong lake breezes, the lakefront itself may actually have lower pollen counts — but surrounding neighborhoods can see spikes. Check wind direction alongside pollen counts when planning outdoor activities.
Chicago's legendary outdoor festival season — from Taste of Chicago in June to Lollapalooza in August to neighborhood street fests throughout summer — coincides directly with grass and early ragweed pollen seasons. If you're attending multi-hour outdoor events in Grant Park, Lincoln Park, or neighborhood venues, premedicate with antihistamines 1–2 hours before, wear sunglasses to protect your eyes from pollen, and shower plus change clothes as soon as you return home. The prolonged outdoor exposure at festivals accumulates far more allergen contact than a typical day.
Unlike southern cities where pollen ramps up gradually, Chicago's pollen season often explodes within days. After a long winter, the first sustained warm spell in late March or April triggers rapid, simultaneous blooming of multiple tree species. Pollen counts can jump from Low to Very High in under a week. Start taking allergy medications by mid-March — before symptoms hit — to give antihistamines and nasal sprays time to build effectiveness. Don't wait until you're already miserable.
Chicago's housing stock includes a significant number of vintage homes and apartment buildings — greystone two-flats, classic six-flats, and pre-war apartments. These buildings often have limited ventilation, older forced-air heating systems, unfinished basements prone to moisture and mold, and layouts that trap dust and allergens. If you live in older Chicago housing, invest in a standalone HEPA air purifier for your bedroom, seal gaps around older windows, and address any basement moisture issues promptly. Cockroach allergens are also more prevalent in older multi-unit buildings — use bait traps and seal entry points around pipes.
Chicago's harsh winters are a silver lining for outdoor allergy sufferers — the months of genuine pollen-free relief are longer than in most major U.S. cities. Use this window to see a board-certified allergist, get tested, and start sublingual immunotherapy. Beginning HeyPak® allergy drops during winter means your immune system has months of desensitization before the spring pollen explosion arrives. Most patients notice improvement within 3–6 months — timing a winter start means you could see meaningful relief by your first spring on treatment.
The Asthma and Allergy Center of Chicago provides the official Chicagoland pollen and mold readings, updated weekday mornings from April through October. These readings are measured directly from the metro area — unlike national forecast sites that use regional modeling. Checking the local count before planning outdoor activities is the single most effective daily habit for managing Chicago allergy symptoms. On Very High count days, limit outdoor time, keep car and home windows closed, and shower before bed.
April through May is typically the worst period, when tree pollen from oak, birch, and maple peaks and overlaps with early grass pollen. September is also severe due to ragweed, which is one of the top allergens in the Chicagoland area. Pollen counts frequently reach "Very High" levels during warm, windy spring days.
Outdoor pollen season runs from approximately March through October, with a genuine winter break after the first hard frost. However, indoor allergens — dust mites, mold, cockroach allergens, and pet dander — intensify during Chicago's long winter when homes are sealed and heated for five months. Many residents experience allergy symptoms in every season.
Yes. Lake Michigan creates rising air currents that can spread and disperse pollen more widely across the metro area. Chicago's wind compounds this by carrying pollen significant distances from parks, trees, and agricultural areas into neighborhoods with minimal vegetation. The lake effect is one reason Chicago's pollen distribution patterns differ from other Midwest cities.
Yes. HeyAllergy provides telemedicine appointments with board-certified allergists licensed in Illinois. You can book a virtual consultation, have allergy blood tests ordered at a local lab, receive a diagnosis, and start treatment — all without visiting a clinic. No waitlist, and appointments are available quickly.
HeyAllergy's HeyPak® sublingual immunotherapy drops are customized based on your blood allergy test results and formulated with allergens specific to the Chicago region — including oak, birch, maple, Timothy grass, ragweed, dust mites, and mold. You place drops under your tongue daily at home. Over 3–6 months, your immune system builds tolerance, reducing symptoms and medication dependence.
HeyAllergy accepts Medicare and most major PPO health plans, including United Healthcare, Anthem Blue Cross, Blue Shield, Cigna, Aetna, Humana, Oscar, and Tricare. Telemedicine benefits vary by plan — contact your insurance provider with HeyAllergy's Tax ID (85-0834175) to confirm your specific coverage.
Ideally, start during winter — Chicago's long cold season provides a pollen-free window to begin sublingual immunotherapy. Starting HeyPak® drops in December through February gives your immune system months of desensitization before the spring pollen explosion in April. For medication-only management, begin antihistamines and nasal sprays by mid-March, before tree pollen arrives.
HeyAllergy has no waitlist. You can book an online appointment at a time that works for you and see a board-certified allergist via secure video consultation — typically within days, not weeks. Available for residents throughout the Chicagoland area, including Cook, DuPage, Lake, Will, and Kane counties.
Chicago occupies a distinctive position on the southwestern shore of Lake Michigan that directly shapes its allergy landscape. The lake's massive surface area creates a meteorological phenomenon known as the "lake effect" — rising air currents from the water spread and disperse pollen more widely across the metro area than in comparable inland cities. Combined with Chicago's well-earned "Windy City" reputation, airborne allergens travel far and fast across the 2.7-million-person city and its sprawling suburbs.
The Chicagoland area sits at the intersection of the Midwest Mississippi Valley allergy region, surrounded by agricultural land that produces its own pollen load. Prevailing winds carry rural grass, weed, and crop pollen into the metro area, layering it on top of the urban pollen produced by the city's 4 million trees, extensive park system, and residential landscaping. The result is an allergy season that's concentrated but intense — Chicago doesn't have year-round pollen like southern cities, but its spring and fall peaks are among the most severe in the Midwest.
Climate data shows that Chicago's allergy seasons have been starting earlier and lasting longer over the past two decades. Warmer springs trigger earlier tree blooming — some years, elm and maple begin pollinating in late February rather than the historical March start. Warmer falls delay the first hard frost that kills ragweed, extending the fall allergy season into late October or even November. The Asthma and Allergy Foundation of America has consistently ranked Chicago among the most challenging cities for allergy sufferers, and the trend is worsening.
Summer temperatures have also been increasing, creating conditions favorable for mold growth. Humidity spikes following Chicago's frequent summer thunderstorms can push mold spore counts to problematic levels, particularly in older buildings with poor ventilation and basements prone to moisture intrusion.
Chicago's park system spans over 8,800 acres and includes iconic spaces like Lincoln Park, Grant Park, Millennium Park, Humboldt Park, and Washington Park. These green spaces are essential to the city's quality of life — but during pollen season, they're concentrated allergen sources. Oak, maple, and birch trees line park pathways, and grass lawns produce significant pollen loads from May through July. The lakefront trail — one of the most popular recreational paths in the country — runs adjacent to heavy tree and grass plantings for most of its 18-mile length.
For the millions of Chicagoans who run, bike, and walk the lakefront trail and neighborhood parks, spring through early fall means direct exposure to the city's highest pollen concentrations. Strategic timing — exercising in late afternoon or evening rather than early morning when pollen peaks — can meaningfully reduce exposure during peak season.
Chicago's housing landscape presents specific indoor allergen challenges. The city's famous greystone buildings, classic two-flats and six-flats, and pre-war apartment stock — while architecturally distinctive — often feature limited ventilation, aging forced-air heating systems, and basements prone to moisture and mold. During Chicago's approximately five-month winter, residents seal windows and run heating systems that circulate dust mites, mold spores, and other allergens throughout living spaces.
Cockroach allergens are a documented problem in Chicago multi-unit housing and a significant contributor to the city's elevated childhood asthma rates. Dust mites flourish in carpeted older apartments. Mold grows in basements and around windows in buildings with deferred maintenance. For many Chicagoans, indoor allergy symptoms peak in winter — the opposite of what most people associate with "allergy season."
Navigating Chicago for medical appointments means contending with some of the worst traffic congestion in the country — whether driving the Kennedy, Eisenhower, or Dan Ryan expressways or waiting for delayed CTA trains. Traditional allergy clinics often have multi-week wait times for new patients, and allergy shot schedules requiring weekly or biweekly visits are difficult to maintain for working professionals battling Chicago commutes.
HeyAllergy eliminates these barriers entirely. Residents throughout Cook, DuPage, Lake, Will, Kane, and McHenry counties can see a board-certified allergist from home via secure video consultation. Comprehensive blood allergy tests can be ordered to a convenient local lab, and a personalized treatment plan — including prescriptions and HeyPak® sublingual immunotherapy drops — can begin without a single in-person visit.
HeyPak® is particularly well-suited for Chicago patients because the drops are customized based on your specific test results and the allergens endemic to the Chicagoland region — including local tree, grass, weed, mold, and indoor triggers. They're mailed directly to your door, taken daily under the tongue, and monitored through follow-up telemedicine visits. No needles, no expressway commute, no waitlist.
If your allergy symptoms persist beyond a few weeks each season, over-the-counter antihistamines aren't providing adequate relief, you experience recurring sinus infections during or after pollen season, allergies are affecting your sleep or work productivity, you have both allergies and asthma, your symptoms seem to worsen every year with Chicago's extending allergy seasons, or you suffer from indoor allergy symptoms throughout the long winter, it's time to see a board-certified allergist.
HeyAllergy accepts Medicare and most major PPO health plans, making expert allergy care accessible for residents throughout the Chicagoland area.
