Mosquito season in Lancaster County, NE: when it starts and ends

Mosquito months in Lancaster County

In a normal year mosquito season in Lancaster County, NE starts around April 15 and ends around October 22, about 27 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 Lancaster County, and when

• Start tipping out standing water weekly by April 1.
• Book any yard treatment for mid April, ahead of the July peak.
• Repellent can go away after October 22.
• 91 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to August, and check NE spray notices.

Lancaster County against the rest of NE

Lancaster County has the 17th longest season of 93 NE counties, at 190 days against 200 in Richardson County and 127 in Sioux County. Its mean temperature is 51.7°F.

• Sarpy County: April 14 to October 22 (191 days, 56 WNV)
• York County: April 14 to October 22 (191 days, 12 WNV)
• Dodge County: April 15 to October 20 (189 days, 29 WNV)
• Saunders County: April 15 to October 20 (189 days, 14 WNV)

West Nile in Lancaster County

From 1999 to 2025, CDC ArboNET counted 314 human West Nile cases in Lancaster County (109 neuroinvasive) across 24 years. The worst was 2003 with 114; the latest was 2025.

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