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

Mosquito months in Brule County

In a normal year mosquito season in Brule County, SD starts around April 25 and ends around October 14, about 24 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 Brule County, and when

• Start tipping out standing water weekly by April 11.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 14.
• 4 West Nile cases since 2016 (last 2022): you should use repellent at dusk July to August, more so if over 60.

Brule County against the rest of SD

Brule County has the 11th longest season of 66 SD counties, at 171 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 47.5°F.

• Bon Homme County: April 24 to October 13 (172 days, 14 WNV)
• Minnehaha County: April 24 to October 13 (172 days, 86 WNV)
• Clay County: April 24 to October 11 (170 days, 8 WNV)
• Lincoln County: April 24 to October 11 (170 days, 39 WNV)

West Nile in Brule County

From 1999 to 2025, CDC ArboNET counted 26 human West Nile cases in Brule County (8 neuroinvasive) across 11 years. The worst was 2003 with 12; the latest was 2022.

See how the dates are worked out, and reading the West Nile counts.