When you are assessing conditions for outdoor painting, consider the temperature, humidity, wind and weather forecast. The recommended temperature for most paints is usually between 50 and 85 degrees Fahrenheit, although some say 90 degrees is the cutoff point. Humidity should be low to help paint dry properly. You don't want to paint in the wind either, as it may blow debris onto the paint and cause the paint to dry too fast. Finally, you want to make sure the paint has at least 24 to 48 hours to dry before it rains.
High temperatures cause the water in the paint to evaporate, which means the paint dries too fast. Paint that dries before it has a chance to adhere to the surface is likely to bubble and peel in the future. Lap marks, which result with you paint over dry paint, are also more common. High temperatures can also prevent the paint from flowing evenly, which causes strokes to appear uneven or creates a rough, crinkled surface on the paint.
Shade can be your best ally and is essential if you must paint when the temperature is above 85 degrees. Sun can increase the surface temperature of your house walls by 10 to 25 degrees Fahrenheit. The north and west sides of your home will have shade in the morning; the south and east sides will be shaded in the late afternoon.
Another major concern with working outdoors during the heat is safety for you, or whoever is doing the painting. Painting your house is hard work and often requires you to climb ladders. It is important not to push yourself too hard and to stay hydrated. Take frequent breaks and stop at the first potential sign of heat stroke, such as headache, dizziness, fatigue, rapid heartbeat, disorientation, sluggishness or high body temperature.