California Mosquito Forecast
California's dry climate — only about 14" of rain a year — keeps mosquito pressure low across most of the state. Numbers climb mainly around irrigated land, standing water near towns, and the days right after a storm, rather than statewide.
Tap any city on the map above, or open the full California map →
When is mosquito season in California?
California's mosquito season runs from April through October. Activity ramps up once overnight lows hold above about 50°F, and surges in the two to three days after rain, when fresh standing water triggers a new hatch. Long dry spells keep a lid on numbers between rain events.
Where are mosquitoes worst in California?
Within California, the most consistent pressure tends to land around Los Angeles, San Diego, and San Jose. In a dry state, the standing water mosquitoes need is concentrated in cities — irrigation, lawns, retention ponds, stormwater — so the metros read higher than the open country around them. Anywhere near rivers, marshes, lakes, or recent flooding will read higher than the surrounding area — exactly the kind of local detail the live map above is built to show.
How the California forecast works
MosquitoCast estimates California's mosquito activity from live weather — temperature, humidity, wind, and recent rainfall — layered on the area's long-term rainfall climate, elevation, and terrain, and refreshed every day from NOAA's forecast data. It's the same model nationwide, so the reading for California is directly comparable to anywhere else in the country.