Nobody can say for sure yet. SoyLei, the maker of the treatment we use, tested it in the lab at about 140°F and has published no field data from Arizona or any desert climate. Dark roofs in Phoenix sun can run hotter than that, so we treat heat as an open question and tell you so.
How hot a Phoenix roof gets
The air alone is rough. Phoenix Sky Harbor’s July average high is 106.5°F (NOAA normals, 1991 to 2020), and the National Weather Service counts an average of 21 days a year at 110°F or above. In 2024 there were 70 of them, a record.
The roof runs hotter than the air. The EPA says standard black asphalt roofs “can reach 165 to 185°F” at midday in summer. That is a national figure, not a Phoenix measurement. Add a summer UV index the EPA lists as 10, or “Very High”, and you have the conditions that dry shingles out. Read more in Arizona heat and asphalt shingles.
What has and hasn’t been tested
In SoyLei’s peer-reviewed paper, treated shingles went into “a 60 °C oven for 48 hours” to simulate a summer roof. That is 140°F. The same paper says “future work should include field validation under natural weathering conditions.” Its authors own shares in SoyLei, so it isn’t independent work.
Shingle makers have concerns of their own. Some, Owens Corning among them, have published bulletins advising against field-applied rejuvenators. Owens Corning’s August 2026 bulletin lists blistering, curling and softening of the asphalt among the possible effects. On a roof that sits in this much heat, that deserves a careful look, and it can affect your shingle warranty.
What that means for your roof
We won’t tell you the treatment was built for the desert. What we will do is look at your roof, tell you whether it is still a fit, and be straight about what is known and what isn’t. Start with our roof rejuvenation page, then book a free roof evaluation when you want an answer for your own roof.