How GoodDayTo judges exterior-painting weather
Exterior painting needs more than a moment without rain. GoodDayTo looks for a practical run of dry hours and also considers humidity, air temperature and wind. High rain probability is penalised strongly, while very humid air, strong wind and temperatures outside a moderate working range lower the score further.
- Rain probability
- Measured precipitation
- Relative humidity
- Air temperature
- Wind speed
- Daylight
🎨 The product label still comes first
- Different paints, stains, primers and sealers have different temperature and humidity limits.
- The wall, wood or metal surface can be hotter, colder or wetter than the reported air.
- Dew, overnight condensation and recent rain can matter even when the forecast currently looks dry.
Why GoodDayTo looks for a dry window
A single dry hour is not very useful if rain is likely before the coating has had time to set. The score therefore gives rain probability a large weight and compares consecutive forecast hours. It also penalises high humidity because slower evaporation can extend drying time, and it reduces the result as wind becomes strong enough to carry dust, leaves or overspray.
A WAIT result can mean conditions improve later in the day, but it can also mean that the forecast never produces a long enough reliable block. Because the model uses a general weather screen, you should compare the suggested window with the minimum application and drying conditions printed by the coating manufacturer.
What temperature does the score prefer?
The model favours moderate temperatures rather than extreme heat or cold. That is intentionally broad because products differ. Direct sunshine can also heat a dark surface well above the air temperature, while shaded masonry can remain cool and damp. GoodDayTo does not pretend the forecast air temperature is the same as the surface temperature.
What the exterior-painting score cannot know
The app cannot measure substrate moisture, dew point at the wall, surface temperature, paint chemistry, number of coats, drying time, shade, dust, pollen or whether the surface was recently pressure washed. It also cannot tell whether a ladder or work area is safe. Treat the result as a weather filter that helps decide whether the day is worth considering, then follow the coating instructions and safe working practices.
What the score means
GO means the forecast has a promising dry, moderate and relatively calm working window. WAIT means conditions are mixed or a better period may arrive later. NOT TODAY means rain risk, humidity, temperature, wind or severe weather currently makes exterior painting a poor weather choice.
Frequently asked questions
What weather is best for exterior painting?
A useful dry spell, moderate temperature, lower humidity and lighter wind are generally more favourable than very hot, wet, humid or windy conditions.
Why can a dry hour still get WAIT?
Exterior painting needs more than one dry moment. GoodDayTo looks for a practical multi-hour window and considers rain probability, humidity, temperature and wind across that period.
Does the score know whether the wall or timber is still damp?
No. A surface can remain damp after earlier rain or dew even when the forecast is now dry. Substrate moisture must be checked separately before painting.
Does wind matter for painting outside?
Yes. Strong wind can carry dust and debris onto wet coatings, affect spraying and speed up surface drying unevenly, so windy conditions reduce the score.
Does GO mean it is safe to apply any paint or stain?
No. Always follow the coating manufacturer’s temperature, humidity, drying-time and surface-preparation instructions. Product requirements override the general weather score.