Is it allergy season in Missouri?

Missouri sits at a geographic crossroads where Southern warmth meets Midwestern agricultural intensity, creating one of the country's most demanding allergy environments. St. Louis consistently appears in AAFA top-5 worst allergy city lists, driven by its position in a major river valley that traps pollen, combined with enormous ragweed production from surrounding farmland. Kansas City experiences similarly high counts, particularly during grass season.

Missouri's two major river corridors — the Mississippi on the east and the Missouri River bisecting the state — create valley trapping effects that concentrate pollen. The Ozark Plateau in the south adds a forested tree pollen layer, while the northern plains closely resemble Iowa and Illinois in their agricultural allergen intensity.

St. Louis Metro

River valley trapping and the nation's worst allergy burden

Positioned at the confluence of the Mississippi and Missouri Rivers, St. Louis sits in a natural pollen trap. The river valleys prevent pollen dispersal on still days. The city ranks in the AAFA top-5 most challenging allergy cities, with particularly severe ragweed in late summer.

Trees · Apr–MayGrass · May–JulRagweed · Aug–Oct (severe)

Kansas City

Western exposure and prairie grass

Kansas City sits at the edge of the Great Plains, exposing it to wind-driven pollen from the west during dry conditions. Grass pollen from the prairie region is particularly intense June–July. Ragweed rivals St. Louis in severity. The urban heat island advances the spring season.

Trees · Apr–MayGrass · Jun–Jul (intense)Ragweed · Aug–Sep

Ozarks

Forested plateau and diverse tree pollen

The Ozark Plateau covers much of southern Missouri with hardwood forests that produce substantial oak and hickory pollen in spring. Springfield sees a heavy tree season followed by a somewhat lighter grass season than the river valleys, but ragweed is still pronounced in fall.

Oak · Apr–May (Ozarks)Trees diverseRagweed · Aug–Sep

Northern Plains

Agricultural belt ragweed intensity

Northern Missouri's flat agricultural landscape mirrors Illinois and Iowa in its allergen profile. Corn and soybean farming contributes to the grass and weed pollen burden. Ragweed production from farmland is intense, with counts peaking in late August through September.

Grass · May–JulRagweed · Aug–Sep (heavy)Agricultural zone

Each row shows a full year of pollen for one region — trees in blue, grasses in green, weeds in amber. Look for where all three rows go quiet at the same time — that's your window.

Oral Allergy Syndrome (also called pollen-food allergy syndrome) causes tingling or mild itching in the mouth when you eat certain raw foods during the relevant pollen season. The proteins in the food are similar enough to the pollen protein that your immune system cross-reacts. Cooking usually deactivates the offending protein, so the same food cooked may cause no reaction.

Oak & Birch pollen

Stone fruits & apples

Apples, peaches, cherries, plums, pears, almonds, hazelnuts, carrots, celery

Peak risk April–May. St. Louis’s river valley position concentrates tree pollen heavily during spring. Peeling fruit removes most of the cross-reactive protein.

Grass pollen

Tomatoes, potatoes & melons

Tomatoes, potatoes, kiwi, watermelon, cantaloupe, oranges (in some cases)

Peak risk May–July. Kansas City and the northern agricultural belt see very high grass counts. St. Louis grass season is also intense.

Ragweed

Melons & bananas

Watermelon, cantaloupe, honeydew, banana, zucchini, cucumber, sunflower seeds

Peak risk August–October. St. Louis is one of America's most ragweed-affected cities. The Missouri River valley traps ragweed pollen on calm autumn evenings.

Not medical advice. If you suspect OAS, speak with an allergist — it can sometimes progress, and symptoms that extend beyond the mouth should be evaluated.