Fall through spring is usually easiest, outside the hottest weeks and outside monsoon season. Summer work is possible, scheduled around the heat for the crew’s sake, and from mid-June to the end of September we plan around storms. SoyLei has published no maximum roof temperature for applying its product, so we don’t claim one.
Heat and the crew
Phoenix heat arrives early and leaves late. The National Weather Service puts the average first 100°F day at May 2 and the last at October 5, using 1991 to 2020 figures. A roof in full sun runs well above the air temperature. The EPA’s national figure for standard black asphalt roofs is 165 to 185°F at midday in summer.
That is hard on the people working up there. In the hot months, jobs start early and aim to wrap up before the worst of the afternoon. It also means you should never climb up to check your own roof on a summer day.
Monsoon season
Monsoon season officially runs June 15 to September 30. The NWS warns that storm outflows “can result in winds 50 mph or greater, and very dense blowing dust.” SoyLei’s application brochure says to check the forecast and confirm “there is no rain, strong wind, or severe weather expected during or after application.”
In monsoon season that can mean moving a date with little warning. A big storm can also lift or tear shingles, and those need a roofer’s repair before any treatment.
Fall through spring
Milder days and fewer storms make dates easier to hold. Phoenix gets only 7.22 inches of rain a year on average, but winter storms happen, so the same forecast check applies.
Read more in Arizona heat and asphalt shingles, and see our monsoon roof check for what to look at after storm season. To pick a date, start with a free roof evaluation.