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

Mosquito months in Buffalo County

In a normal year mosquito season in Buffalo County, SD starts around April 28 and ends around October 9, about 23 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 Buffalo County, and when

• Start tipping out standing water weekly by April 14.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 9.
• 2 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.

Buffalo County against the rest of SD

Buffalo County has the 24th longest season of 66 SD counties, at 164 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 45.8°F.

• Oglala Lakota County: April 30 to October 12 (165 days, 9 WNV)
• Beadle County: April 27 to October 8 (164 days, 32 WNV)
• Hand County: April 29 to October 9 (163 days, 6 WNV)
• Ziebach County: April 29 to October 9 (163 days, 2 WNV)

West Nile in Buffalo County

From 1999 to 2025, CDC ArboNET counted 11 human West Nile cases in Buffalo County (5 neuroinvasive) across 6 years. The worst was 2003 with 5; the latest was 2023.

Background: when mosquitoes go away for the winter; how the dates are worked out.