Mosquito season in Riley County, KS: when it starts and ends

Mosquito months in Riley County

In a normal year mosquito season in Riley County, KS starts around April 10 and ends around October 28, about 29 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Riley County, and when

• Start tipping out standing water weekly by March 27.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after October 28.
• 1 West Nile case since 2016 (last 2022): you should use repellent at dusk June to August, more so if over 60.

Riley County against the rest of KS

Riley County has the 65th longest season of 105 KS counties, at 201 days against 227 in Cherokee County and 178 in Thomas County. Its mean temperature is 54.4°F.

• Leavenworth County: April 9 to October 27 (201 days, 2 WNV)
• Reno County: April 10 to October 28 (201 days, 11 WNV)
• Nemaha County: April 9 to October 26 (200 days, 0 WNV)
• Clark County: April 10 to October 27 (200 days, 0 WNV)

West Nile in Riley County

From 1999 to 2025, CDC ArboNET counted 7 human West Nile cases in Riley County (3 neuroinvasive) across 6 years. The worst was 2003 with 2; the latest was 2022.

Background: when the season starts across the US; how the dates are worked out.