California Allergy Season Guide

California experiences a Mediterranean climate with mild, wet winters and warm, dry summers along the coast, with hotter inland valleys.

Oak, olive, cypress, and acacia tree pollen are the largest spring triggers. Bermuda and rye grass extend the season into summer, and ragweed plus sagebrush are the late-summer weeds.

Coastal humidity supports year-round Cladosporium and Alternaria. Fall and winter rain events drive the strongest spore peaks.

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