Mosquito season in Belknap County, NH: when it starts and ends
Mosquito months in Belknap County
In a normal year mosquito season in Belknap County, NH starts around April 30 and ends around October 13, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Belknap County, and when
- Start tipping out standing water weekly by April 16.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 13.
- No West Nile cases since 2016, so bites in Belknap County are a nuisance; check window screens.
Belknap County against the rest of NH
Belknap County has the 3rd longest season of 10 NH counties, at 166 days against 170 in Strafford County and 141 in Coos County. Its mean temperature is 46.5°F.
- Strafford County: April 28 to October 14 (170 days, 0 WNV)
- Rockingham County: April 28 to October 14 (169 days, 2 WNV)
- Hillsborough County: April 30 to October 11 (164 days, 0 WNV)
- Cheshire County: May 2 to October 10 (161 days, 1 WNV)
West Nile in Belknap County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Belknap County (1 neuroinvasive) across 1 year. The worst was 2003 with 1; the latest was 2003.
See how the dates are worked out, and when the season starts across the US.