Colorado Allergy Season Guide

Colorado experiences a high-elevation semi-arid to alpine climate with cold winters, warm dry summers, and dramatic day-night temperature swings.

Juniper, cedar, and cottonwood drive an early-spring tree season. Grasses peak in early summer and sagebrush is the dominant fall weed.

Mold counts are typically lower at altitude but spike after monsoon storms and irrigated agricultural cycles in the lower valleys.

Allergy patterns vary by elevation and proximity to coast or mountains within Colorado, but most of the state shares a common seasonal rhythm of spring tree pollen, summer grass pollen, and late-summer to fall weed pollen.