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

Mosquito months in Butler County

In a normal year mosquito season in Butler County, KS starts around April 3 and ends around November 2, about 30 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 Butler County, and when

• Start tipping out standing water weekly by March 20.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after November 2.
• 6 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to September, more so if over 60.

Butler County against the rest of KS

Butler County has the 21st longest season of 105 KS counties, at 213 days against 227 in Cherokee County and 178 in Thomas County. Its mean temperature is 56.4°F.

• Linn County: April 2 to November 1 (213 days, 1 WNV)
• Osage County: April 2 to November 1 (213 days, 0 WNV)
• Barber County: April 2 to October 31 (212 days, 3 WNV)
• Cowley County: April 3 to November 1 (212 days, 3 WNV)

West Nile in Butler County

From 1999 to 2025, CDC ArboNET counted 14 human West Nile cases in Butler County (7 neuroinvasive) across 10 years. The worst was 2012 with 3; the latest was 2025.

More: how the dates are worked out · reading the West Nile counts.