Mosquito season in Roberts County, SD: when it starts and ends
Mosquito months in Roberts County
In a normal year mosquito season in Roberts County, SD starts around April 29 and ends around October 8, about 23 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Roberts 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 8.
- 5 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.
Roberts County against the rest of SD
Roberts County has the 31st longest season of 66 SD counties, at 162 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 43.9°F.
- Todd County: May 1 to October 11 (163 days, 3 WNV)
- McCook County: April 29 to October 8 (162 days, 9 WNV)
- Kingsbury County: April 29 to October 8 (161 days, 17 WNV)
- Perkins County: May 1 to October 9 (161 days, 1 WNV)
West Nile in Roberts County
From 1999 to 2025, CDC ArboNET counted 39 human West Nile cases in Roberts County (6 neuroinvasive) across 11 years. The worst was 2003 with 17; the latest was 2025.
See how the dates are worked out, and reading the West Nile counts.