Denver, CO Pollen Levels Today

Denver's high-altitude, semi-arid climate along the Front Range creates a distinct and often intense allergy profile, with dry winds from the plains and mountains capable of carrying pollen over long distances and prolonging exposure.

Tree pollen season typically begins in late February and runs through May, driven by cottonwood, juniper, cedar, elm, ash, maple, and oak, with peaks in April when multiple species release simultaneously. Grass pollen takes over from mid-May through July, with Kentucky bluegrass—widely planted in local lawns—alongside timothy, brome, and orchard grass as the dominant triggers.

Weed season follows from August through the first hard frost in October, led by ragweed, sagebrush, Russian thistle (tumbleweed), kochia, and pigweed, all well-adapted to Colorado's dry conditions.

Late spring often brings overlapping tree and grass pollen, while late summer can layer grass and early weed pollen, intensifying symptoms during transition periods.

Non-pollen allergens also play a meaningful role: dust stirred up by chinook winds, outdoor molds after monsoon moisture, and ozone pollution trapped by the Front Range can all worsen reactions.

Overall, Denver's allergy profile is defined by a long, wind-driven season, diverse weed exposure, and environmental irritants amplified by the region's dryness and elevation.