Mild
Mild pollen — sensitive individuals may notice
Weed pollen is the main trigger · Tomorrow → · Updated 15 hours ago
Today in St. Louis: weed pollen is moderate, tree pollen is low, grass pollen is none. Overall score: 32/100. Allergies are mild right now; sensitive people may notice symptoms. Tomorrow is expected to be about the same. Updated at 1:00 AM.
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Pollen levels in St. Louis are currently low. Most people should not experience allergy symptoms from pollen.
Tree pollen: Low. Grass pollen: None. Weed pollen: Moderate.
Tomorrow's pollen forecast for St. Louis is expected to be about the same, with mild pollen conditions.
Weed pollen is the highest supported pollen type in St. Louis today. Weed pollen is moderate.
Tree pollen in St. Louis is low today.
Grass pollen in St. Louis is none today.
Weed pollen in St. Louis is moderate today.
Tomorrow's pollen forecast for St. Louis is expected to be about the same, with mild pollen conditions.
Situated in the humid continental climate of the Mississippi and Missouri River confluence, St. Louis consistently ranks among the more challenging U.S. cities for seasonal allergies. The region's long growing season, high summer humidity, and riverine geography create conditions that sustain airborne allergens nearly year-round.
Tree pollen kicks off the allergy calendar in late February and peaks from March through May, with oak, maple, cedar, elm, sycamore, hickory, and cottonwood serving as the most prolific local offenders. As tree counts taper, grass pollen takes over from May into July, dominated by Kentucky bluegrass, timothy, orchard grass, and Bermuda.
By mid-August, weed season ramps up and runs through the first hard frost in October or November, with ragweed as the primary culprit alongside lamb's quarters, pigweed, and plantain. The overlap between lingering grasses and early ragweed in August often intensifies symptoms for sensitized residents.
Beyond pollen, St. Louis's humidity fuels persistent outdoor and indoor mold, particularly Alternaria and Cladosporium, while dust mites thrive in muggy summers and the city's ozone and particulate pollution can compound respiratory irritation.
Overall, St. Louis's allergy profile is defined by extended seasons, heavy ragweed exposure, and mold-amplifying humidity.