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Exterior Painting Weather in Illinois: Best Months by City

Exterior Painting season in Illinois, city by city: peak months, season boundaries, and annual workable-day counts from NOAA 1991–2020 normals. Alton leads with 160 workable days a year; Waukegan runs the shortest at 110.

Across Illinois's 15 listed cities, annual workable days for exterior painting run from 110 (Waukegan) up to 160 (Alton). Every number comes from NOAA 1991–2020 normals scored against the same label ruleset; every city name links to its live 10-day check.

If one month anchors the Illinois calendar it's August, the statewide leader in workable days. Use this page to pick the month, then the city page's 10-day strip to pick the days — and the national exterior painting guide for the physics behind each rule.

Cities in Illinois

Peak months and season boundaries from NOAA 1991–2020 normals; season = months with at least 8 workable days.
CityPeak monthsSeasonWorkable days/yr
Chicago Aug, Jul, Sep April–October 133
Rockford Aug, Jul, Sep May–October 123
Round Lake Beach Aug, Jul, Sep May–October 124
Peoria Aug, Sep, Jul April–October 137
Aurora Aug, Jul, Sep May–October 127
Springfield Aug, Sep, Jul April–October 133
Champaign Aug, Sep, Jul April–October 130
Naperville Aug, Jul, Sep May–October 129
Joliet Aug, Sep, Jul May–October 128
Bloomington Jul, Aug, Sep May–October 126
Elgin Aug, Jul, Sep May–October 116
Waukegan Jul, Aug, Sep May–October 110
Cicero Aug, Jul, Sep April–October 133
Alton Aug, Jul, Sep April–October 160
Decatur Aug, Sep, Jul April–October 141

The rules behind these numbers

Typical label thresholds for exterior painting — the single ruleset used by every check on this page.
CheckThresholdWhy it matters
Air temperature 50–90°F (low-temp formulas from 35°F) Standard latex wants 50°F+. Some low-temperature formulas are rated down to 35°F.
Overnight low ≥35°F during the first 24 h (≥40°F preferred) Paint keeps curing overnight; a low under 40°F stalls standard latex.
Dry before ≤0.05" rain in the prior 12 h; watch back to 24 h The surface must be dry to the touch and out of a recent soak.
Dry after <0.05" rain for 24 h after Rain inside the first 24 hours can streak or wash fresh paint.
Evening dew-point spread ≥5°F from 6–11 pm Surface should stay at least 5°F above the dew point; dew flat-spots fresh paint.
Daytime humidity ≤80% High humidity extends recoat and cure times.
Wind ≤15 mph (brush only up to 20 mph) Wind dries the leading edge too fast and carries overspray.

Always follow your product label — formulas vary. The table above is the typical range across major manufacturers, not a promise about your can.

Other tasks in Illinois

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