Right now in Costa Mesa, the air is about 73°F, but the model estimates the asphalt under your dog's paws is closer to 79°F — a gap of roughly 6°F, because heavy cloud cover is taking some of the edge off the direct sun. That reading puts Costa Mesa 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 5 hours left today, the pavement in Costa Mesa is projected to top out near 79°F around 7 PM, when the air will be about 73°F — a 7°F gap between the forecast your weather app shows and the surface your dog walks on. The surface is already coming down, about 10°F over the next three hours, so waiting a little works in your favour here.
In an average August, Costa Mesa sees highs around 76°F and overnight lows near 64°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.
Costa Mesa 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 76°F against 62°F in March, a 14°F swing that decides how much of the day belongs to your dog.
Costa Mesa sits about 5 miles from Huntington Beach, 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 Costa Mesa 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.