Mosquito season in Sussex County, DE: when it starts and ends
Mosquito months in Sussex County
In a normal year mosquito season in Sussex County, DE starts around March 28 and ends around November 13, about 33 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Sussex County, and when
- Start tipping out standing water weekly by March 14.
- Book any yard treatment for late March, ahead of the July peak.
- Repellent can go away after November 13.
- 6 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to September, more so if over 60.
Sussex County against the rest of DE
Sussex County has the 1st longest season of 3 DE counties, at 230 days against 230 in Sussex County and 215 in New Castle County. Its mean temperature is 57.6°F.
- Kent County: March 30 to November 11 (226 days, 4 WNV)
- New Castle County: April 4 to November 5 (215 days, 14 WNV)
West Nile in Sussex County
From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Sussex County (5 neuroinvasive) across 8 years. The worst was 2018 with 2; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.