Fort Collins, CO Pollen Levels Today

Fort Collins sits along the Front Range at the edge of the Rocky Mountains, where a semi-arid climate, strong Chinook winds, and wide temperature swings combine to create a long and often intense allergy season.

Tree pollen kicks things off in early spring, typically from March through May, with cottonwood, aspen, box elder, juniper, elm, ash, and Siberian elm as the most prominent local culprits.

As trees taper off, grass pollen surges from late May through July, driven largely by Kentucky bluegrass, Timothy, orchard grass, and brome, which thrive in irrigated lawns, parks, and the foothills' open meadows.

Late summer through the first hard frost brings the weed season, generally August through October, dominated by ragweed, sagebrush, Russian thistle (tumbleweed), kochia, lamb's quarters, and pigweed. Overlap between lingering grasses and early weeds in August often intensifies symptoms for multi-sensitive individuals.

Beyond pollen, Fort Collins' dry air stirs up significant dust and particulate matter, while wildfire smoke drifting from regional fires has become an increasingly common irritant. Indoor and outdoor mold spikes after spring snowmelt and summer thunderstorms, and occasional ozone pollution adds further strain.

Overall, Fort Collins' allergy profile is defined by windy, dry conditions, robust weed pressure, and a prolonged pollen calendar.