All 50 states

Long pollen season with high tree and grass counts across the southeast.

Short but intense spring birch and alder season.

Year-round allergens including juniper, mesquite and palo verde.

High oak and cedar pollen in spring; ragweed dominates fall.

Diverse microclimates drive long, overlapping pollen seasons.

Dry climate amplifies juniper and grass pollen along the Front Range.

Northeastern hardwood and grass pollen peaks late spring.

Coastal humidity raises mold; oak and grass peak in spring.

Twelve-month pollen season; oak, grass and ragweed dominate.

Famous for spring pine pollen along with high oak counts.

Year-round grass pollen with periodic mold spikes.

Sagebrush, juniper and grass dominate the Mountain West.

Strong ragweed season; oak and grass in spring.

Midwestern grass and ragweed dominate.

Heavy agricultural ragweed and grass season.

Plains ragweed, grass and cedar drive long allergy season.

Bluegrass capital; ragweed and mold also strong.

Mold and ragweed are persistent; oak peaks in spring.

Birch and grass pollen drive a short, intense season.

Mid-Atlantic mix of oak, grass and ragweed.

Northeastern hardwood and grass pollen.

Birch and ragweed lead a Great Lakes pollen season.

Short but strong birch and ragweed cycles.

Long, humid season; mold and oak dominate.

Ragweed and grass dominate; oak peaks in spring.

Sagebrush and grass on the plains; pine in the mountains.

Plains ragweed is intense in fall.

High desert juniper and sagebrush; mulberry in urban areas.

Birch and grass pollen typical of New England.

Dense oak and grass pollen across the corridor.

Juniper, mulberry and elm dominate.

Oak, birch and ragweed lead a strong allergy season.

Famous pine pollen; oak and grass also high.

Plains grass and ragweed.

Strong ragweed; oak and grass spring peaks.

Cedar fever in winter; ragweed in fall.

Grass seed capital; alder and birch in spring.

Oak, maple and ragweed lead Appalachian pollen.

Coastal mix of oak, grass and ragweed.

Pine and oak pollen are intense in spring.

Plains grass and ragweed.

Persistent oak, grass and ragweed.

Cedar fever in winter; ragweed and grass through fall.

Juniper, sagebrush and Russian thistle dominate.

Maple, birch and grass.

Heavy oak and pine; ragweed in fall.

Alder and grass dominate Pacific Northwest.

Appalachian oak and ragweed.

Birch, ragweed and grass.

Sagebrush and grass at high elevation.