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

Mosquito months in Monmouth County

In a normal year mosquito season in Monmouth County, NJ starts around April 11 and ends around November 2, 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 Monmouth County, and when

• Start tipping out standing water weekly by March 28.
• Book any yard treatment for mid April, ahead of the July peak.
• Repellent can go away after November 2.
• 25 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to August, and check NJ spray notices.

Monmouth County against the rest of NJ

Monmouth County has the 11th longest season of 21 NJ counties, at 205 days against 217 in Cape May County and 184 in Sussex County. Its mean temperature is 53.9°F.

• Cumberland County: April 10 to November 2 (206 days, 5 WNV)
• Middlesex County: April 10 to November 1 (205 days, 20 WNV)
• Mercer County: April 10 to October 30 (204 days, 9 WNV)
• Essex County: April 11 to October 28 (199 days, 10 WNV)

West Nile in Monmouth County

From 1999 to 2025, CDC ArboNET counted 42 human West Nile cases in Monmouth County (28 neuroinvasive) across 17 years. The worst was 2022 with 5; the latest was 2025.

More: how the dates are worked out · reading the West Nile counts.