Mosquito season in Beadle County, SD: when it starts and ends
Mosquito months in Beadle County
In a normal year mosquito season in Beadle County, SD starts around April 27 and ends around October 8, about 23 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Beadle County, and when
- Start tipping out standing water weekly by April 13.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 8.
- 32 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check SD spray notices.
Beadle County against the rest of SD
Beadle County has the 23rd longest season of 66 SD counties, at 164 days against 179 in Yankton County and 139 in Lawrence County. Its mean temperature is 45.9°F.
- Sully County: April 29 to October 11 (165 days, 3 WNV)
- Oglala Lakota County: April 30 to October 12 (165 days, 9 WNV)
- Buffalo County: April 28 to October 9 (164 days, 2 WNV)
- Hand County: April 29 to October 9 (163 days, 6 WNV)
West Nile in Beadle County
From 1999 to 2025, CDC ArboNET counted 88 human West Nile cases in Beadle County (19 neuroinvasive) across 19 years. The worst was 2003 with 16; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.