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

Mosquito months in Lawrence County

In a normal year mosquito season in Lawrence County, SD starts around May 15 and ends around October 1, about 20 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 Lawrence County, and when

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

Lawrence County against the rest of SD

Lawrence County has the 66th longest season of 66 SD counties, at 139 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 44.1°F.

• Hughes County: May 8 to October 2 (147 days, 24 WNV)
• Custer County: May 11 to October 4 (146 days, 0 WNV)

West Nile in Lawrence County

From 1999 to 2025, CDC ArboNET counted 44 human West Nile cases in Lawrence County (5 neuroinvasive) across 13 years. The worst was 2003 with 27; the latest was 2025.

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