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

Mosquito months in Codington County

In a normal year mosquito season in Codington County, SD starts around May 2 and ends around October 6, about 22 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 Codington County, and when

• Start tipping out standing water weekly by April 18.
• Book any yard treatment for early May, ahead of the July peak.
• Repellent can go away after October 6.
• 25 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to July, and check SD spray notices.

Codington County against the rest of SD

Codington County has the 54th longest season of 66 SD counties, at 157 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 42.8°F.

• Stanley County: May 1 to October 5 (157 days, 4 WNV)
• Clark County: May 2 to October 6 (157 days, 11 WNV)
• Day County: May 2 to October 6 (157 days, 10 WNV)
• Edmunds County: May 2 to October 5 (156 days, 10 WNV)

West Nile in Codington County

From 1999 to 2025, CDC ArboNET counted 64 human West Nile cases in Codington County (11 neuroinvasive) across 19 years. The worst was 2018 with 8; the latest was 2025.

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