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

Mosquito months in Hanson County

In a normal year mosquito season in Hanson County, SD starts around April 30 and ends around October 7, 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 Hanson County, and when

• Start tipping out standing water weekly by April 16.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 7.
• 5 West Nile cases since 2016 (last 2022): you should use repellent at dusk July to July, more so if over 60.

Hanson County against the rest of SD

Hanson County has the 38th longest season of 66 SD counties, at 160 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 45.1°F.

• Corson County: April 30 to October 7 (160 days, 3 WNV)
• Dewey County: April 30 to October 7 (160 days, 11 WNV)
• Spink County: April 30 to October 7 (160 days, 21 WNV)
• Grant County: May 1 to October 8 (160 days, 7 WNV)

West Nile in Hanson County

From 1999 to 2025, CDC ArboNET counted 22 human West Nile cases in Hanson County (5 neuroinvasive) across 10 years. The worst was 2005 with 6; the latest was 2022.

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