Riverside, CA Pollen Levels Today

Riverside, CA sits in the Inland Empire, where a semi-arid Mediterranean climate, mild winters, and hot dry summers create an extended and often intense allergy season.

Tree pollen kicks off the year early, typically from February through May, with olive, mulberry, oak, sycamore, ash, and juniper as dominant local contributors—olive and mulberry are especially problematic despite longstanding planting restrictions.

As trees taper, grass pollen surges from April into July, driven largely by Bermuda grass, along with ryegrass, fescue, and Johnson grass; Bermuda in particular can linger well into early fall due to the region's warm temperatures.

Weed season follows in late summer through November, featuring ragweed, Russian thistle (tumbleweed), sagebrush, pigweed, and lamb's quarters, with peaks typically in September and October.

Overlap between late-spring trees and early grasses, as well as between summer grasses and emerging weeds, often intensifies symptoms for multi-sensitive individuals.

Non-pollen triggers are also significant: dry, dusty Santa Ana winds stir up particulates, regional air pollution and ozone levels rank among the highest in the nation, and indoor and outdoor molds thrive after seasonal rains.

Overall, Riverside's allergy profile is defined by a long pollen calendar, persistent grasses, and air-quality factors that amplify exposure year-round.