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

Mosquito months in Johnson County

In a normal year mosquito season in Johnson County, KS starts around April 1 and ends around November 1, about 31 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 Johnson County, and when

• Start tipping out standing water weekly by March 18.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after November 1.
• 25 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to August, and check KS spray notices.

Johnson County against the rest of KS

Johnson County has the 15th longest season of 105 KS counties, at 214 days against 227 in Cherokee County and 178 in Thomas County. Its mean temperature is 55.1°F.

• Comanche County: April 3 to November 5 (216 days, 0 WNV)
• Sumner County: April 3 to November 5 (216 days, 1 WNV)
• Coffey County: April 2 to November 2 (214 days, 0 WNV)
• Dickinson County: April 2 to November 2 (214 days, 6 WNV)

West Nile in Johnson County

From 1999 to 2025, CDC ArboNET counted 71 human West Nile cases in Johnson County (58 neuroinvasive) across 22 years. The worst was 2013 with 6; the latest was 2025.

Background: reading the West Nile counts; how the dates are worked out.