In the Desert region, cedar, ash and oak pollinate from February to April. Other allergy-causing trees include the cypress, mesquite, ash and olive.

The grass season for this region can last from April until October. The primary allergenic grasses for the region are brome, Bermuda, salt grass, rye, Canary grass, and June grass.

Weeds in the region pollinate from March to December, including the ragweed, chenopod and sage. Other weeds that can trigger allergies include the carelessweed, iodine bush, saltbush/scale, lamb's-quarter and Russian thistle.