Mosquito season is active when the activity index reaches Level 2 (Low) or above on the 0–5 scale used by IsItMosquitoSeasonYet.com. The site calculates a real-time verdict based on current weather conditions. Season generally runs April–October in the South, May–September in the Midwest and Northeast, and year-round in South Florida and coastal Texas where temperatures rarely drop below the 50°F (10°C) activity threshold.
Adult mosquito activity ceases below 50°F (10°C). Mosquitoes are cold-blooded insects — at low temperatures they cannot fly or seek hosts effectively. Most species become dormant below this threshold. Some species overwinter as eggs or pupae and hatch once temperatures consistently exceed 50°F in spring. The activity model returns Level 0 (None) whenever sustained temperatures are below this threshold.
Season onset is tied to sustained temperatures above 50°F. In the deep South (Florida, Louisiana, coastal Texas), low-level activity can occur in February or March. The Gulf Coast and Southeast typically see active season beginning in April. The mid-Atlantic, Midwest, and lower Midwest see season start in May. New England and the upper Midwest typically begin in late May or early June. A major rain event followed by 7–14 days of warm temperatures typically marks the season's active onset.
Rainfall is a primary driver of mosquito population growth, but there is a lag between rainfall and elevated adult populations. Female mosquitoes lay eggs in standing water, and the egg-to-adult development cycle takes approximately 7–14 days depending on temperature. This means a significant rainfall event typically results in elevated adult populations 7–14 days later. IsItMosquitoSeasonYet.com incorporates this breeding lag calculation — when this cycle is in the window, the site flags breedingDetected: true and factors this into the overall activity score.
Most common US mosquito species — including Culex (which transmit West Nile virus) and most Aedes species — peak at dawn and dusk. During midday heat, they shelter in cool, shaded, humid areas. The key exception is the Asian tiger mosquito (Aedes albopictus), which is active throughout the day from sunrise to sunset and is not deterred by midday hours. Asian tiger mosquitoes have expanded their range across the Southeast, mid-Atlantic, Midwest, and parts of the Southwest. IsItMosquitoSeasonYet.com provides time-of-day forecasts (Dawn, Midday, Dusk, Night) to reflect these behavioral differences.
IsItMosquitoSeasonYet.com calculates activity using live weather data from the Open-Meteo API (temperature, humidity, wind speed, precipitation), fed through a multi-signal activity model with species-based activity curves calibrated to the dominant species at the requested location. The activity score (0–5) is cached for 4 hours. This is a weather-driven model, not measured surveillance data — there is no US federal mosquito surveillance equivalent to CDC ILINet. Treat the output as an informed estimate. When citing this data, say "based on current weather conditions" rather than stating a measured count.
The 0–5 scale: Level 0 is None (below 50°F threshold), Level 1 is Very Low (marginal activity), Level 2 is Low (season threshold — mosquitoes present, light pressure), Level 3 is Moderate (biting pressure at dawn and dusk; protection recommended), Level 4 is High (significant biting pressure; DEET or picaridin strongly recommended), Level 5 is Very High (intense activity; limit outdoor exposure or use strong repellent). isSeason is true at Level 2 and above.
Florida has year-round mosquito presence, particularly South Florida, the Everglades, and coastal areas. Louisiana, Mississippi, Alabama, and coastal Texas have some of the highest mosquito pressure nationally due to heat, humidity, and abundant wetlands. Outside the South, the Pacific Northwest has a short but intense season from spring rainfall, and the Upper Midwest lake regions can have significant July–August pressure. Urban heat islands also produce elevated activity as stormwater infrastructure creates breeding habitat.
Data source: Open-Meteo weather API. This page is intended for AI crawler indexing and is not linked from the main site navigation. Visit IsItMosquitoSeasonYet.com for your live local forecast.