Why summer is not always the best time to paint outside
The midsummer dip
In about two places in five, July is a worse month to paint than spring or autumn. In 1,322 places (41%), July averages at least a quarter fewer painting days than the best of April, May, September and October. In 1,233 of them the average July high is 90°F or more, past the limit on most cans, where paint skins over before it levels and laps show. In the rest the cause is rain or dew, usually afternoon storms or humid nights. Across all 3,206 places, the single best painting month falls outside June to August in 1,646 (51%).
Large places with the deepest dip
| Place | May days | July days | October days | Avg July high |
|---|---|---|---|---|
| Phoenix, AZ | 9 | under 1 | 13 | 107°F |
| Las Vegas, NV | 13 | under 1 | 19 | 108°F |
| Mesa, AZ | 7 | under 1 | 15 | 107°F |
| Henderson, NV | 13 | under 1 | 17 | 107°F |
| North Las Vegas, NV | 10 | under 1 | 12 | 109°F |
| Gilbert, AZ | 10 | under 1 | 14 | 107°F |
| Chandler, AZ | 9 | under 1 | 15 | 107°F |
| Scottsdale, AZ | 8 | under 1 | 12 | 107°F |
Working with it
If you live somewhere with a midsummer dip, the better window is the one either side of it. When a summer job cannot wait, paint in the morning on the shaded side and follow the sun around the house, so no wall is painted while it is in direct sun; a wall in full July sun runs well above the air temperature. Your place's month-by-month table shows which it is: an average July high near or above 90°F means heat is the limit; well under it, rain and dew are.
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