Mosquito season in Union County, SC: when it starts and ends

Mosquito months in Union County

In a normal year mosquito season in Union County, SC starts around March 24 and ends around November 10, about 33 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 Union County, and when

• Start tipping out standing water weekly by March 10.
• Book any yard treatment for late March, ahead of the July peak.
• Repellent can go away after November 10.
• 2 West Nile cases since 2016 (last 2018): you should use repellent at dusk June to September, more so if over 60.

Union County against the rest of SC

Union County has the 44th longest season of 46 SC counties, at 231 days against 349 in Charleston County and 209 in Cherokee County. Its mean temperature is 61.1°F.

• Chesterfield County: March 21 to November 13 (237 days, 0 WNV)
• Spartanburg County: March 24 to November 11 (232 days, 4 WNV)
• Oconee County: March 30 to November 9 (224 days, 0 WNV)
• Cherokee County: April 6 to November 1 (209 days, 1 WNV)

West Nile in Union County

From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Union County (3 neuroinvasive) across 3 years. The worst was 2018 with 1; the latest was 2018.

Background: when the season starts across the US; how the dates are worked out.