Washington Mosquito Forecast

Washington's winters shut mosquito activity down for months — but snowmelt and standing water then drive a sharp surge from June through August. Pressure is low-to-moderate across the calendar as a whole, yet spikes hard at the peak.

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When is mosquito season in Washington?

Washington's mosquito season runs from June through August. 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. The window is short, but it can be relentless while it lasts.

Where are mosquitoes worst in Washington?

Within Washington, the most consistent pressure tends to land around Seattle, Spokane, and Tacoma. Low, wet ground near these areas turns spring snowmelt and rain into prime breeding habitat. 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 Washington forecast works

MosquitoCast estimates Washington'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 Washington is directly comparable to anywhere else in the country.