Painting in humid weather: how Madison summers change the job

What humidity does to wet paint

Latex paint dries as its water evaporates. Dunn-Edwards says that when humidity is high, coatings are exposed to more water vapor, so it takes longer for the water in latex paint to leave. Dark colors take longer to dry and cure than light ones, higher-gloss paints take longer to cure than low-sheen ones, and a room with poor air circulation makes all of it worse.

Slow drying has a visible cost. When latex paint dries slowly in damp air, surfactants (the soap-like ingredients that keep paint stable) can rise to the surface and leave glossy, tan or brown streaks. Dunn-Edwards notes this can happen on interior latex paint in places that see high moisture, like bathrooms. If it shows up in the first few days, the streaks can usually be cleaned off, and the bulletin says they don't threaten the durability of the paint film. Our guide to choosing bathroom wall paint covers how to keep them off fresh walls.

What a Madison summer looks like to a painter

The Wisconsin State Climatology Office's 1991 to 2020 normals show how summer sits in Madison. June is the wettest month of the year, and July and August aren't far behind.

Warm air holds more water vapor, and when it cools at night that moisture shows up as dew and clammy surfaces. After a day in the 80s with a night near 60°F, fresh paint can stay slow to dry. Whether the moisture comes off a lake or out of a thunderstorm, paint responds to the same thing: how much water is in the air and how close the temperature is to the dew point.

Keep indoor humidity in range

The EPA's guide to mold and moisture says to keep indoor relative humidity below 60 percent, ideally between 30 and 50 percent. It suggests using air conditioners and dehumidifiers when needed, venting moisture-producing appliances to the outdoors, and running the bathroom fan or opening a window when showering. It also says condensation on windows, walls or pipes is a sign of high humidity.

That advice carries straight over to painting:

• Run the air conditioner or a dehumidifier the day before painting, while the paint is wet, and for the days afterward.
• Keep the bathroom fan running, and skip long hot showers in a bathroom with fresh paint.
• Use a dehumidifier in a basement, where damp walls are the usual problem. Our post on basement painting ideas covers the rest.
• Use a humidity meter to see what you're dealing with, since it's hard to judge by feel.

Rooms that need extra care

Some rooms are damp all year, and summer makes it worse. Bathrooms and laundry rooms are the obvious ones, with kitchens and basements close behind. Our guide to painting a bathroom covers moisture and mildew.

Cabinets are an indoor job that also feels humidity. Refinishing takes one to two weeks for most kitchens, and that includes drying time between coats. A very muggy stretch can lengthen the waits, which is a good question to raise on the estimate call. Our post on how long cabinet painting takes shows where the time goes.

Colors and sheens that dry slower

Two choices you make at the paint counter affect how a humid week goes. According to Dunn-Edwards, dark colors that carry a lot of pigment take longer to dry and cure than light colors, and the colorants in them can slow curing further. Higher-gloss coatings also cure more slowly than low-sheen ones.

That doesn't mean you should avoid deep colors or a glossy trim finish. It means a deep navy on a muggy week deserves more patience between coats than a pale gray does. Our guide to paint sheens helps you pick a finish, and our guide to choosing a cabinet color shows how color looks on real kitchens.

How to tell paint isn't drying right

• It's still tacky well past the usual recoat time.
• Glossy, tan or brown streaks appear, often running down from the top of a wall.
• Paint sags or runs. Diamond Vogel says excess moisture in the air can make fresh paint sag and run as well as dry slowly.
• Water drips or beads on the surface when it should be drying.

If you see any of these, stop. Don't recoat tacky paint, bring the humidity down, and let the surface dry fully before you decide what to do. Call us if you're not sure, and don't scrub before asking, since the right cleanup depends on the surface and the paint.

Outdoors in humid weather

Exterior paint has less margin than interior paint, because you can't control the air. Diamond Vogel's technical bulletin on exterior latex says not to apply paint if the air temperature is less than 5°F above the dew point, if moisture is forming on the surface or nearby surfaces, if humidity is 90 percent or higher and the temperature is expected to fall, or if rain is forecast within eight hours.

Dunn-Edwards adds that you shouldn't paint a day before or after rain is forecast, or late in the day when dew may be present. We schedule doors, trim and decks around dry weather for the same reasons. Our post on how long deck stain needs to dry shows how humidity stretches each wait. Our post on Madison's outdoor painting season explains the temperature side, and our decks and exterior painting page lists what we do outside.

Timing a job in humid weather

1. Check the forecast for the day of the job and the days after, including the dew point if your weather app shows it.
2. Start the air conditioner or dehumidifier the day before, so the room is already dry when the first coat goes on.
3. Start early, so each coat has the whole day to dry before the evening air turns damp.
4. Allow the long end of the typical range between coats. Dunn-Edwards puts a latex recoat at two to four hours under good conditions, and humidity stretches that.
5. Plan for a long cure. The same bulletin says latex takes 14 to 30 days to fully cure.

Our post on dry time versus cure time explains why a surface that feels dry still needs gentle treatment for weeks.

Planning an interior job in summer

Floors and furniture are covered first, small holes are repaired, and most rooms take one to two days. Interior painting is priced by the square footage of the space, paint included. The written quote is the price, no extra charge if the job takes longer than expected. That matters in a week when the drying takes longer than planned.

To talk through a room, a kitchen or a basement, ask for a free estimate. We cover Madison and the towns around it, and our interior painting page lists everything we do indoors. If you're planning for the colder months instead, see our post on painting in winter.