The best time to paint outside is largely dependent on the weather. Paint won’t adhere as smoothly or dry properly if the temperatures are too hot or too cold.
Very hot temperatures can cause paint to dry too fast, or not adhere well in the first place leaving you with unsightly cracks and blisters on the surface you’re trying to paint.
So, when is it too hot to paint outside? To answer that question we’ll look at several factors that impact painting outside including how and why temperature affects paint drying, why paint needs time to dry properly, what is the ideal temperature for painting outside, and other weather conditions that can impact drying.
Why Does Temperature Matter when Painting Outside?
Outside temperatures can make a huge difference in the quality of your finished paint job because air temperature has a big impact on how paint dries.
How quickly the paint dries impacts how even and smooth the paint job will appear. In ideal temperatures paint can be applied evenly and dry properly for a smooth finish.
If the temperature is too hot or too cold the paint will dry too fast or too slow leading to problems like cracking, blistering, visible brush marks, uneven coats, and peeling paint.
What’s the Ideal Outdoor Temperature Range when Using Exterior Paint?
To figure out when is it too hot to paint outside we’ll first need to know what the ideal temperature range is for exterior paints.
Different kinds of paints dry at different rates so the ideal temperature can vary depending on what type of paint you use.
Latex paints work best when they are applied at temperatures between fifty and eighty-five degrees.
Oil based paints have a broader range and can be applied in temperatures from forty to ninety degrees.
Depending on the type of paint you have, an outside temperature over eighty-five to ninety degrees is too hot to paint outside.
What is Paint Curing and Why do I Need to Know About it?
Paint curing and paint drying are actually two different things. You need both to happen properly for the best quality paint job and both are impacted by how hot it is outside when you paint.
Paint Curing Vs. Paint Drying
Paint drying happens first and is much quicker than curing. As paint dries, the water and solvents evaporate from the applied paint and it will feel dry to the touch. At this point the paint is still soft and easily damaged.
Paint curing happens when the applied paint chemically bonds with the surface making it hard and strong. When curing is complete, paint is 100%, fully dry and has reached maximum hardness. This usually takes around two weeks.
Once paint is fully cured, it will be much more durable and can be washed and touched without messing up your new paint.
How High Heat Impacts Drying and Curing
Very high temperatures can cause the surface of the paint to dry very fast, causing the paint to look and feel dry when the lower layers are not yet dry.
Drying too fast can lead to cracks, bumps, blisters, and discoloration because the paint won’t adhere properly and the lower layers of paint won’t dry evenly.
Drying too fast can also lead to visible brush marks and uneven coats because the strokes won’t blend well when paint is starting to dry while you’re still applying it.
In extreme heat (or extreme cold) the chemical reactions required for curing may be slowed down considerably. This means it can take much longer for your paint to cure leaving the paint vulnerable to damage. Even if the paint is dry, you still need it to cure properly for a long lasting, high quality finish.
Ways Weather Can Affect Painting Outside
You already have a head start on planning by thinking about when is it too hot to paint outside. It may be helpful to think about how other weather conditions can affect painting outside as well.
How Wind Affects Paint
Too much wind will cause paint to dry too quickly. Paint contains binding agents to help it bond to the surface you are painting. When paint dries fast, those binding agents evaporate too quickly which prevents your paint from adhering to the surface correctly.
Wind can negatively impact your paint job even in cold weather. Wind causes evaporation by moving air quickly over the surface. Evaporation happens even if the air is cold. Think about hand dryers, the air blowing out is often not very warm but it still dries your hands. Wind works on your painted surface much the same way.
Another issue with wind is things blowing around. Sediment and leaves can be blown up into your paint both in the paint tray or bucket and on the surface you’re painting.
How Rain Affects Paint
Rain can cause a lot of issues when painting outside both before and after you paint. Too much moisture will keep paint from adhering and drying properly.
It is very important that your surfaces are dry before painting to get a good bond of paint to the surface. If there has been any rain recently, you may need to wait a few days until everything has dried fully before applying paint.
After applying paint, you will need at least four to eight hours without rain for the paint to dry properly.
How Humidity Affects Paint
Too much or too little moisture in the air can cause issues with paint drying as well.
If the humidity is too high, paint may not adhere as well causing bubbles and eventually peeling and flaking once it’s dry. High humidity also slows down the drying process. If you’ve ever tried to dry clothes outdoors on a humid day, you know how humidity can affect drying! It’s the same way with paint.
If the humidity is too low, the paint may dry too fast which can lead to cracks, blisters and other issues we’ve already discussed.
A humidity level between forty to fifty percent is an ideal range. If that’s not possible, you can still paint in humidity up to seventy percent for a smooth and even appearance, but it may take longer to dry.
Other Considerations When Painting Outside
The Effects of Direct Sunlight
Direct sunlight is another factor that can cause problems with drying. Heat from the sun, even when the air temperatures are not that high, can cause paint to dry too quickly leading to problems like visible brush marks, cracks, and bubbles.
Work with What You Have
Plan the paint job so that you’ll be painting sunny areas of the house in the early morning hours before the sun is too strong or the temperatures are too high. Then when the sun is at it’s strongest you can paint shaded areas of the house.
Check Your Paint Can
Different paints have different guidelines for ideal temperatures and dry time so make sure to read the label on your paint can to get information on when is it too hot to paint outside for your specific type of paint.
Final Thoughts on When is it Too Hot to Paint Outside
With that information you should have a better understanding of when is it too hot too paint outside and why paint doesn’t go on or dry as well in high temperatures. For more information on when you should and shouldn’t paint outside, check out this article on when is the best time to paint an exterior. If you’re wondering whether you should hire a painter or do the work yourself, this article has some helpful information.