Right now in Rialto, the air is about 77°F, but the model estimates the asphalt under your dog's paws is closer to 77°F — the surface and air have nearly converged because the pavement is shedding the day's stored heat after dark. That reading puts Rialto in the clear for an ordinary walk. Air temperature alone would have told you none of this — the pavement, not the forecast, is what your dog actually stands on.
Across the 21 hours left today, the pavement in Rialto is projected to top out near 158°F around 2 PM, when the air will be about 106°F — a 51°F gap between the forecast your weather app shows and the surface your dog walks on. Today breaks into 2 separate safe stretches rather than one continuous window, so missing the first does not cost you the day.
In an average August, Rialto sees highs around 96°F and overnight lows near 70°F. At highs like that, sun-baked pavement can easily top 120–130°F by early afternoon, so the walkable hours cluster around dawn and after sunset. As a seasonal rule of thumb, the safest windows are before about 9:00 AM and after about 6:00 PM.
Rialto loses its all-day safe window in 7 months of the year — April through October — and August is one of them. The year peaks in August at an average high of 96°F against 62°F in January, a 34°F swing that decides how much of the day belongs to your dog.
Rialto sits about 4 miles from Fontana, close enough that the two usually run within a degree or two of each other — if your walk crosses between them, either page answers the question. Street-level conditions still differ more than city-level ones do: a shaded side street and an open parking lot half a block apart can be twenty degrees apart underfoot.
Whatever the number says, confirm it with your hand: press the back of it flat on the pavement for seven seconds. If you can't hold it there, neither can your dog. Conditions in Rialto are on the gentler side right now, but keep the same habits: water before and after, grass over asphalt, and a close eye on flat-faced breeds, seniors, and puppies, who overheat and burn sooner than a healthy adult dog.