Mosquito season in Jefferson County, KS: when it starts and ends
Mosquito months in Jefferson County
In a normal year mosquito season in Jefferson County, KS starts around April 7 and ends around October 30, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Jefferson County, and when
- Start tipping out standing water weekly by March 24.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 30.
- 1 West Nile case since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Jefferson County against the rest of KS
Jefferson County has the 41st longest season of 105 KS counties, at 206 days against 227 in Cherokee County and 178 in Thomas County. Its mean temperature is 54.5°F.
- Saline County: April 7 to October 31 (207 days, 9 WNV)
- Wabaunsee County: April 6 to October 29 (206 days, 1 WNV)
- Stafford County: April 7 to October 30 (206 days, 4 WNV)
- Seward County: April 9 to November 1 (206 days, 2 WNV)
West Nile in Jefferson County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Jefferson County (1 neuroinvasive) across 1 year. The worst was 2025 with 1; the latest was 2025.
See how the dates are worked out, and when mosquitoes go away for the winter.