Mosquito season in Sussex County, NJ: when it starts and ends
Mosquito months in Sussex County
In a normal year mosquito season in Sussex County, NJ starts around April 19 and ends around October 20, about 26 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 April 5.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 20.
- 2 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to August, more so if over 60.
Sussex County against the rest of NJ
Sussex County has the 21st longest season of 21 NJ counties, at 184 days against 217 in Cape May County and 184 in Sussex County. Its mean temperature is 49.9°F.
- Morris County: April 18 to October 22 (188 days, 8 WNV)
- Warren County: April 18 to October 21 (186 days, 7 WNV)
West Nile in Sussex County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Sussex County (0 neuroinvasive) across 3 years. The worst was 2025 with 1; the latest was 2025.
Background: when the season starts across the US; how the dates are worked out.