Arizona Allergy Season Guide

Arizona experiences a hot, arid desert climate with long dry summers, mild winters, and very low annual rainfall.

Tree pollen — especially mulberry, olive, ash, juniper, and mesquite — is the dominant trigger in late winter and early spring. Bermuda grass is the most common warm-season grass, and ragweed and tumbleweed (Russian thistle) drive the late-summer through fall load.

Outdoor mold counts in the desert are generally lower than in humid regions, but Alternaria and Cladosporium spikes follow monsoon storms in July and August, and indoor mold is common where evaporative cooling, leaks, or irrigation overspray create damp microclimates.

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