As a rule of thumb, the sunnier the day, the better it is for painting. That’s why you’re starting to see painting crews take on both exterior and interior projects more frequently now that the days are getting longer and warmer. Still, even in the summer, there are good days for painting and bad days for painting.

The main issue for painting inside or outside is moisture. We don’t have to worry too much about humidity here in Colorado, but on cloudy days with the threat of thunderstorms, when there’s more moisture in the air than normal, the paint and the surface it’s going on will be affected.

Moisture thins paint and makes it runnier. This can be a good thing if your paint is old and dry, but in most cases, it can cause uneven finishes on exteriors and interiors.

Exterior paint jobs obviously are more affected by the weather. If there’s moisture in the air, or, God forbid, a thunderstorm washes through, the paint can run or be washed right off the exterior of your house, even if you use primer and scrape old paint off. You’ll notice on cloudy days the paint doesn’t dry as quickly and might be a little easier to spread over the surface.

Interior painting projects can turn ugly fast in bad weather, too. If it’s pouring down rain outside, inner areas won’t be as ventilated and could have problems drying, leading to excess paint fumes indoors. The outside humidity can creep inside as well.

There’s an ideal painting weather day. If the temperature outside is too hot, the paint could dry irregularly and have trouble spreading evenly. For example, I once painted a house in 90-degree weather. Granted, I wasn’t a very skilled painter at the time (about ten years ago), but I had trouble getting an even spread on areas that required a brush, like trim, especially when it was directly exposed to the sun.

I’ve never tried to paint anything in the rain or high humidity, but I can’t imagine it being very productive or fun.

Then there’s the health factors. I know from experience that painting an exterior on a hot day costed me seemingly endless gallons of sweat and a sunburn. If you’re not careful, working on high ladders on a hot day can turn into a dangerous situation. Heat stroke is easier than you think to happen to you, especially at altitude. Combine dizziness, disorientation, and spotty vision with a high ladder and a bad situation can turn much worse.

As I alluded to earlier, interior projects can turn dangerous too because of paint fumes. Make sure that your indoor space has plenty of ventilation before you start using anything with hazardous chemicals, like paint.

So, the perfect painting weather day is not too hot, not too cold, with low humidity. If you’re prepared, you can still turn in a good day painting even on very warm days, just be careful out there.