Is it good to paint in San Francisco, CA this week?
A live 7-day go/no-go calendar for exterior paint in San Francisco, 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°F
- Overnight dew
- High
- Rain
- 1%
- Window
- —
High condensation risk overnight — surface dips to within 0°F of the 55°F dew point (low 54°F, 100% cloud, 6 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
- Dew margin
- 0°F
- Overnight dew
- High
- Rain
- 1%
- Window
- —
High condensation risk overnight — surface dips to within 0°F of the 55°F dew point (low 54°F, 100% cloud, 9 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
- Dew margin
- 5.1°F
- Overnight dew
- Low
- Rain
- 0%
- Window
- —
Humidity peaks at 98% — well above the 85% ceiling; cure stalls and moisture gets trapped.
- Dew margin
- 12.2°F
- Overnight dew
- Low
- Rain
- 2%
- Window
- 8am–5pm
Hot afternoon (87°F, ceiling 85°F) — paint early and follow the shade.
- Dew margin
- 9.9°F
- Overnight dew
- Low
- Rain
- 3%
- Window
- 8am–5pm
Clear to paint: temps 70–83°F, RH under 37%, surface stays 9.9°F+ above the dew point, no rain in the cure window.
- Dew margin
- 8.4°F
- Overnight dew
- Low
- Rain
- 1%
- Window
- 8am–5pm
Clear to paint: temps 68–84°F, RH under 49%, surface stays 8.4°F+ above the dew point, no rain in the cure window.
- Dew margin
- 12.7°F
- Overnight dew
- Low
- Rain
- 0%
- Window
- 8am–5pm
Clear to paint: temps 68–81°F, RH under 49%, surface stays 12.7°F+ above the dew point, no rain in the cure window.
- High condensation risk overnight — surface dips to within 0°F of the 55°F dew point (low 54°F, 100% cloud, 6 mph wind). A fresh paint can blush/blister. Stop 4h before dew falls.
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.