Mosquito season in Linn County, IA: when it starts and ends
Mosquito months in Linn County
In a normal year mosquito season in Linn County, IA starts around April 17 and ends around October 21, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Linn County, 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 21.
- 4 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Linn County against the rest of IA
Linn County has the 26th longest season of 99 IA counties, at 187 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 49.7°F.
- Ringgold County: April 16 to October 20 (187 days, 0 WNV)
- Appanoose County: April 17 to October 21 (187 days, 1 WNV)
- Dallas County: April 16 to October 19 (186 days, 0 WNV)
- Adair County: April 17 to October 20 (186 days, 0 WNV)
West Nile in Linn County
From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Linn County (4 neuroinvasive) across 8 years. The worst was 2002 with 2; the latest was 2025.
See how the dates are worked out, and reading the West Nile counts.