Wisconsin pest season calendar
Wisconsin's cold winters push several pests indoors for shelter, while spring and summer bring the outdoor season. These windows are keyed to University of Wisconsin-Madison Extension research, not a marketing calendar.
| Pest | Peak window | What it means for you | Source |
|---|---|---|---|
| Boxelder bugs | fall through early spring | Boxelder bugs gather on warm walls in fall, then move indoors to overwinter. Seal cracks around windows and doors in fall, and vacuum rather than crush any that appear inside. | UW-Madison Extension (Wisconsin Horticulture) |
| Cluster flies | fall through early spring | Cluster flies enter buildings in fall through cracks and holes to overwinter in attics and wall voids. Seal those entry points, and vacuum or sweep up the sluggish flies that emerge on warm days. | UW-Madison Extension (Learning Store) |
| Ticks | spring peak | Spring is peak tick activity in the Midwest. Avoid weedy trail-edge vegetation, wear long sleeves, use EPA-registered repellents, and do daily tick checks after time outdoors. | UW-Madison Extension (Wisconsin Horticulture) |
| Mosquitoes | spring through summer | Mosquitoes are a regular nuisance during Wisconsin's outdoor spring and summer months. Dump standing water weekly; larvae can develop in as little as one inch of water. | UW-Madison Extension (Wisconsin Horticulture) |
Windows are general guidance from the cited university extension and state sources, checked on 2026-08-13. Local weather and microclimate shift them, so treat these as planning ranges rather than exact dates.
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