Mosquito season in Middlesex County, NJ: when it starts and ends

Mosquito months in Middlesex County

In a normal year mosquito season in Middlesex County, NJ starts around April 10 and ends around November 1, about 29 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 Middlesex County, and when

• Start tipping out standing water weekly by March 27.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after November 1.
• 20 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to August, and check NJ spray notices.

Middlesex County against the rest of NJ

Middlesex County has the 10th longest season of 21 NJ counties, at 205 days against 217 in Cape May County and 184 in Sussex County. Its mean temperature is 53.8°F.

• Bergen County: April 9 to November 2 (208 days, 31 WNV)
• Cumberland County: April 10 to November 2 (206 days, 5 WNV)
• Monmouth County: April 11 to November 2 (205 days, 25 WNV)
• Mercer County: April 10 to October 30 (204 days, 9 WNV)

West Nile in Middlesex County

From 1999 to 2025, CDC ArboNET counted 34 human West Nile cases in Middlesex County (28 neuroinvasive) across 17 years. The worst was 2018 with 5; the latest was 2025.

Background: reading the West Nile counts; how the dates are worked out.