Pollen Count & Forecast for St. Louis

St. Louis’s spring allergy season (March-May) is dominated by Oak (Quercus) and Maple (Acer) pollen; Oak prolific in Forest Park and Tower Grove Park; American Elm (Ulmus americana) widespread across city streets. Summer (May-July) sees high Grass (Poaceae) pollen levels, originating from Mississippi River floodplains and Carondelet Park. Late summer (August-October) has high Ragweed (Ambrosia) counts from the Missouri River basin.

Humid air and low-lying river valleys trap pollen near the surface; the confluence of two major rivers maintains high moisture levels. Late autumn sees elevated Mould (Alternaria, Cladosporium) spore counts, from decaying leaf litter in the Missouri Botanical Garden and wooded suburban corridors.