Right now in San Diego, the air is about 86°F, but the model estimates the asphalt under your dog's paws is closer to 126°F — a gap of roughly 40°F, because clear skies are pouring full sun onto every dark surface. That reading puts San Diego in the danger range, where pavement can scald paw pads in under a minute. Humidity is nudging the human "feels-like" to about 92°F, which matters for your dog too: muggy air makes it harder for a panting dog to shed heat, so treat a borderline reading as the hotter of the two.
Across the 13 hours left today, the pavement in San Diego is projected to top out near 139°F around 2 PM, when the air will be about 89°F — a 51°F gap between the forecast your weather app shows and the surface your dog walks on. The surface is still gaining — up about 13°F over the next three hours — so a walk taken now is cooler than the same walk later this afternoon.
In an average August, San Diego sees highs around 78°F and overnight lows near 66°F. Those are forgiving numbers, but don't let them lull you — a sunny, still afternoon can still heat dark asphalt far above the air, especially for low-riding or short-coated dogs. As a seasonal rule of thumb, the safest windows are before about 11:00 AM and after about 4:00 PM.
San Diego loses its all-day safe window in 5 months of the year — May through September — and August is one of them. The year peaks in September at an average high of 78°F against 63°F in March, a 15°F swing that decides how much of the day belongs to your dog.
San Diego sits about 7 miles from Chula Vista, 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. On a day reading this warm in San Diego, flat-faced breeds like pugs and bulldogs, plus seniors and young puppies with thinner pads, should sit out the heat entirely — subtract about 10°F from any safe threshold for them. If you must cross hot ground, protective booties or a quick coat of paw wax are the only real barrier between paw pads and the asphalt.