Is it good to paint in St. Louis, MO this week?
A live 7-day go/no-go calendar for exterior paint in St. Louis, 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
- 13.8°F
- Overnight dew
- Low
- Rain
- 5%
- Window
- —
Too hot — high of 93°F is well over the 85°F ceiling; the film skins over before it can level or adhere.
- Dew margin
- 3.3°F
- Overnight dew
- Watch
- Rain
- 70%
- Window
- —
Rain likely in the 24h cure window (70% chance, ~2.4mm) — it can wash out or mar an uncured paint.
- Dew margin
- 5.9°F
- Overnight dew
- Low
- Rain
- 55%
- Window
- 2pm–5pm
High humidity (86%, over the 85% mark) slows drying — keep an eye on the cure window.
- Dew margin
- 3.7°F
- Overnight dew
- High
- Rain
- 5%
- Window
- —
High condensation risk overnight — surface dips to within 3.7°F of the 42°F dew point (low 45°F, 5% cloud, 5 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
- Dew margin
- 7°F
- Overnight dew
- Low
- Rain
- 1%
- Window
- 8am–5pm
Clear to paint: temps 62–79°F, RH under 45%, surface stays 7°F+ above the dew point, no rain in the cure window.
- Dew margin
- 6°F
- Overnight dew
- Low
- Rain
- 0%
- Window
- 8am–5pm
Clear to paint: temps 55–69°F, RH under 60%, surface stays 6°F+ above the dew point, no rain in the cure window.
- Dew margin
- 20.1°F
- Overnight dew
- Low
- Rain
- 1%
- Window
- 8am–5pm
Clear to paint: temps 51–71°F, RH under 51%, surface stays 20.1°F+ above the dew point, no rain in the cure window.
- Too hot — high of 93°F is well over the 85°F ceiling; the film skins over before it can level or adhere.
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.
Free in the beta
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.