Right now in Boulder, the air is about 80°F, but the model estimates the asphalt under your dog's paws is closer to 110°F — a gap of roughly 30°F, because clear skies are pouring full sun onto every dark surface. That reading puts Boulder 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 14 hours left today, the pavement in Boulder is projected to top out near 137°F around 1 PM, when the air will be about 93°F — a 44°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, Boulder sees highs around 85°F and overnight lows near 59°F. Even at those moderate highs, a dark surface in direct sun can run 40–60°F hotter than the air, which is enough to tip midday walks into the caution range. As a seasonal rule of thumb, the safest windows are before about 11:00 AM and after about 5:00 PM.
Boulder loses its all-day safe window in 4 months of the year — June through September — and August is one of them. The year peaks in July at an average high of 86°F against 37°F in February, a 49°F swing that decides how much of the day belongs to your dog.
The nearest place we track is Westminster, about 17 miles away. That is close enough to move together in a heat wave but far enough that a passing cloud bank or a coastal breeze can put real distance between the two readings, so check Boulder's own page rather than assuming.
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 Boulder 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.