Mosquito season in Minnehaha County, SD: when it starts and ends

Mosquito months in Minnehaha County

In a normal year mosquito season in Minnehaha County, SD starts around April 24 and ends around October 13, about 25 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 Minnehaha County, and when

• Start tipping out standing water weekly by April 10.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 13.
• 86 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check SD spray notices.

Minnehaha County against the rest of SD

Minnehaha County has the 10th longest season of 66 SD counties, at 172 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 46.5°F.

• Davison County: April 23 to October 14 (174 days, 14 WNV)
• Bon Homme County: April 24 to October 13 (172 days, 14 WNV)
• Brule County: April 25 to October 14 (171 days, 4 WNV)
• Clay County: April 24 to October 11 (170 days, 8 WNV)

West Nile in Minnehaha County

From 1999 to 2025, CDC ArboNET counted 215 human West Nile cases in Minnehaha County (73 neuroinvasive) across 21 years. The worst was 2003 with 57; the latest was 2025.

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