Mosquito season in Grand Isle County, VT: when it starts and ends
Mosquito months in Grand Isle County
In a normal year mosquito season in Grand Isle County, VT starts around April 27 and ends around October 15, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Grand Isle County, and when
- Start tipping out standing water weekly by April 13.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 15.
- 2 West Nile cases since 2016 (last 2017): you should use repellent at dusk July to July, more so if over 60.
Grand Isle County against the rest of VT
Grand Isle County has the 2nd longest season of 14 VT counties, at 171 days against 171 in Chittenden County and 144 in Orleans County. Its mean temperature is 46.7°F.
- Chittenden County: April 27 to October 14 (171 days, 2 WNV)
- Addison County: April 30 to October 11 (164 days, 1 WNV)
- Franklin County: May 4 to October 10 (159 days, 0 WNV)
West Nile in Grand Isle County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Grand Isle County (1 neuroinvasive) across 1 year. The worst was 2017 with 2; the latest was 2017.
More: how the dates are worked out · when mosquitoes go away for the winter.