Mosquito season in Boise County, ID: when it starts and ends
Mosquito months in Boise County
In a normal year mosquito season in Boise County, ID starts around May 21 and ends around September 27, about 18 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Boise County, and when
- Start tipping out standing water weekly by May 7.
- Book any yard treatment for late May, ahead of the July peak.
- Repellent can go away after September 27.
- No West Nile cases since 2016, so bites in Boise County are a nuisance; check window screens.
Boise County against the rest of ID
Boise County has the 30th longest season of 44 ID counties, at 129 days against 194 in Canyon County and 85 in Fremont County. Its mean temperature is 42°F.
- Butte County: May 13 to October 1 (141 days, 0 WNV)
- Jefferson County: May 14 to September 21 (130 days, 0 WNV)
- Bonneville County: May 19 to September 23 (127 days, 0 WNV)
- Clearwater County: May 18 to September 20 (125 days, 0 WNV)
West Nile in Boise County
From 1999 to 2025, CDC ArboNET counted 7 human West Nile cases in Boise County (1 neuroinvasive) across 2 years. The worst was 2006 with 6; the latest was 2008.
Background: when the season starts across the US; how the dates are worked out.