Is it good to paint in Chicago, IL this week?
A live 7-day go/no-go calendar for exterior paint in Chicago, built from the local forecast against the 5°F-above-dew-point rule. We lead with the signal a weather app misses: overnight condensation risk.
- Dew margin
- 0.9°F
- Overnight dew
- High
- Rain
- 54%
- Window
- —
High condensation risk overnight — surface dips to within 0.9°F of the 69°F dew point (low 68°F, 100% cloud, 6 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
- Dew margin
- 0.6°F
- Overnight dew
- High
- Rain
- 44%
- Window
- —
High condensation risk overnight — surface dips to within 0.6°F of the 71°F dew point (low 70°F, 100% cloud, 11 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
- Dew margin
- 2.1°F
- Overnight dew
- High
- Rain
- 69%
- Window
- —
High condensation risk overnight — surface dips to within 2.1°F of the 70°F dew point (low 72°F, 16% cloud, 6 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
- Dew margin
- 6.5°F
- Overnight dew
- Low
- Rain
- 54%
- Window
- 8am–5pm
Some rain risk (54%) during the cure window — re-check the radar before you start.
- Dew margin
- 11.2°F
- Overnight dew
- Low
- Rain
- 5%
- Window
- 8am–5pm
Clear to paint: temps 71–74°F, RH under 59%, surface stays 11.2°F+ above the dew point, no rain in the cure window.
- Dew margin
- 1.5°F
- Overnight dew
- High
- Rain
- 27%
- Window
- —
High condensation risk overnight — surface dips to within 1.5°F of the 67°F dew point (low 69°F, 47% cloud, 3 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
- Dew margin
- 6.9°F
- Overnight dew
- Low
- Rain
- 28%
- Window
- 9am–5pm
High humidity (87%, over the 85% mark) slows drying — keep an eye on the cure window.
- High condensation risk overnight — surface dips to within 0.9°F of the 69°F dew point (low 68°F, 100% cloud, 6 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
- Humidity peaks at 98% — well above the 85% ceiling; cure stalls and moisture gets trapped.
- Rain likely in the 24h cure window (54% chance, ~12.9mm) — it can wash out or mar an uncured paint.
Hold off. These are forecast numbers — confirm the surface temperature on-site before you start.
Why these thresholds
Overnight dew condensing on a fresh coat causes blistering, surfactant leaching and peeling — the cause of 40%+ of exterior paint failures.
- • Surface temp must stay 5°F above the dew point through application and cure (ASTM D3276 / ISO 8502-42).
- • Air + surface in the 50–85°F band (low-temp lines to 35°F).
- • Humidity under 85%; ideally under 70%.
- • No rain for 24h after application.
- • We use the forecast ground-surface temperature as a surface-temp proxy — confirm on-site with an IR thermometer.
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Watch this job site 24/7
Get an email the moment overnight dew, rain, or an out-of-range stretch threatens a fresh coat — and a morning digest with the best window ahead. No app to check; we watch the forecast for you.