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

Mosquito months in Morrill County

In a normal year mosquito season in Morrill County, NE starts around April 29 and ends around October 13, about 24 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 Morrill County, and when

• Start tipping out standing water weekly by April 15.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 13.
• 12 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check NE spray notices.

Morrill County against the rest of NE

Morrill County has the 81st longest season of 93 NE counties, at 167 days against 200 in Richardson County and 127 in Sioux County. Its mean temperature is 49.4°F.

• Scotts Bluff County: April 28 to October 12 (167 days, 50 WNV)
• Chase County: April 29 to October 13 (167 days, 7 WNV)
• Arthur County: April 30 to October 12 (165 days, 0 WNV)
• Box Butte County: May 1 to October 10 (163 days, 11 WNV)

West Nile in Morrill County

From 1999 to 2025, CDC ArboNET counted 43 human West Nile cases in Morrill County (8 neuroinvasive) across 16 years. The worst was 2003 with 7; the latest was 2025.

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