Mosquito season in Lower Connecticut River Valley Planning Region, CT: when it starts and ends

Mosquito months in Lower Connecticut River Valley Planning Region

In a normal year mosquito season in Lower Connecticut River Valley Planning Region, CT starts around April 17 and ends around October 25, about 27 weeks.

What to do in Lower Connecticut River Valley Planning Region, and when

Start tipping out standing water weekly by April 3.
Book any yard treatment for mid April, ahead of the July peak.
Repellent can go away after October 25.
1 West Nile case since 2016 (last 2024): you should use repellent at dusk July to August, more so if over 60.

Lower Connecticut River Valley Planning Region against the rest of CT

Lower Connecticut River Valley Planning Region has the 5th longest season of 9 CT counties, at 191 days against 200 in Greater Bridgeport Planning Region and 164 in Northwest Hills Planning Region. Its mean temperature is 51.4°F.

Southeastern Connecticut Planning Region: April 18 to October 28 (193 days, 2 WNV)
South Central Connecticut Planning Region: April 19 to October 29 (192 days, 5 WNV)
Naugatuck Valley Planning Region: April 20 to October 23 (187 days, 0 WNV)
Western Connecticut Planning Region: April 19 to October 22 (186 days, 10 WNV)

West Nile in Lower Connecticut River Valley Planning Region

From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Lower Connecticut River Valley Planning Region (1 neuroinvasive) across 1 year. The worst was 2024 with 1; the latest was 2024.

See how the dates are worked out, and when the season starts across the US.