September Mosquito & Tick Report — Long Island
September marks the transition from peak summer mosquito season to elevated fall tick season. Mosquito pressure declines steadily as temperatures cool, but deer tick adult activity increases significantly. September is often the most overlooked month for pest control — homeowners with wooded properties remain at significant tick risk through the entire fall.
September Activity Summary
🦟 Mosquito Activity
Moderate
🕷️ Tick Activity
Very High
Suffolk County Rainfall
3.0–3.9 inches typical for September (Suffolk County)
Nassau County Rainfall
2.8–3.6 inches typical for September (Nassau County)
🦟 Mosquito Activity — September
Mosquito activity declines noticeably in September. Culex pipiens populations drop sharply after the first frost and begin entering diapause (winter dormancy) once nighttime temperatures consistently fall below 50°F. Warm September days with temperatures above 75°F can still produce localized active periods, particularly near standing water. Most homeowners see a 60–70% reduction in mosquito encounters compared to July.
🕷️ Tick Activity — September
September is the beginning of peak adult deer tick season — which runs through November and into mild December weather. Adult blacklegged ticks become highly active as they seek their final blood meal before winter. This is the second most dangerous tick window of the year (after June nymph season). Properties with deer activity, leaf litter, and wooded edges see heavy adult tick pressure throughout September and October.
Active Species This Month
Culex pipiens (Northern House Mosquito)
Declining sharply. Still active on warm days above 65°F.
Aedes albopictus (Asian Tiger Mosquito)
Largely inactive. Sensitive to cool temperatures.
Ixodes scapularis (Deer Tick)
Peak adult activity. Second-highest Lyme disease risk window of the year.
Amblyomma americanum (Lone Star Tick)
End of season. Minimal activity.
Towns Seeing Elevated Activity in September
September Prevention Recommendations
- Do not skip fall tick treatment — adult deer tick season is September–November
- Rake leaf litter away from the property perimeter — ticks harbor in moist leaves
- Treat wooded edges and stone walls where ticks wait for passing hosts
- Check pets and family members for ticks after every outdoor activity
- Continue mowing through the season — tall grass is prime tick habitat
- Consider a late-season tick spray treatment before October
Looking Ahead
October and November remain high-risk months for deer tick encounters. Tick activity continues until a hard freeze establishes — typically late November to December on Long Island. Homeowners should not assume tick risk ends with the summer season.
This report contains seasonal activity estimates based on historical Long Island mosquito and tick patterns, typical weather conditions, and regional environmental factors. It is not a government health advisory, live surveillance data, or a guarantee of specific conditions. For public health information about mosquito-borne illness in New York State, visit the NYS Department of Health website.