Boise, ID Pollen Levels Today

Boise's high-desert climate, situated in the Treasure Valley between the Boise Foothills and the Snake River Plain, produces a long and often intense allergy season shaped by dry air, irrigated agriculture, and temperature inversions that trap airborne particles.

Tree pollen typically kicks off in late February and peaks from March through May, with juniper and cedar leading early, followed by cottonwood, poplar, birch, elm, maple, ash, and oak—many of which line the Boise River Greenbelt and residential neighborhoods.

As trees taper in late May, grass pollen surges and often dominates through July, driven primarily by timothy, orchard, rye, Kentucky bluegrass, and Bermuda grass, all common in the region's extensive lawns, pastures, and hayfields. The transition between tree and grass seasons frequently overlaps in May, intensifying symptoms for many residents.

Weed pollen takes over from August into October, with Russian thistle (tumbleweed), sagebrush, kochia, pigweed, lamb's quarters, and ragweed being the main culprits across the surrounding sagebrush steppe.

Beyond pollen, Boise's dry, dusty conditions contribute to year-round irritation from windblown dust, wildfire smoke in late summer, and indoor mold in basements and irrigated areas.

Overall, Boise's allergy profile is defined by prolonged exposure, high pollen diversity, and dust-driven aggravation.