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

Mosquito months in Haakon County

In a normal year mosquito season in Haakon County, SD starts around April 29 and ends around October 11, 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 Haakon County, and when

• Start tipping out standing water weekly by April 15.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 11.
• 1 West Nile case since 2016 (last 2025): you should use repellent at dusk July to August, more so if over 60.

Haakon County against the rest of SD

Haakon County has the 19th longest season of 66 SD counties, at 165 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 47.2°F.

• Miner County: April 27 to October 11 (167 days, 5 WNV)
• Lake County: April 27 to October 10 (166 days, 11 WNV)
• Jerauld County: April 29 to October 10 (165 days, 5 WNV)
• Sully County: April 29 to October 11 (165 days, 3 WNV)

West Nile in Haakon County

From 1999 to 2025, CDC ArboNET counted 15 human West Nile cases in Haakon County (4 neuroinvasive) across 4 years. The worst was 2003 with 9; the latest was 2025.

Background: when the season starts across the US; how the dates are worked out.