How we estimate pavement heat
PawForecast answers one question — is it too hot to walk my dog right now?— by estimating the temperature of the pavement under a dog's paws, not just the air temperature. Here's exactly how, and where the numbers come from.
The core idea: air temperature isn't paw temperature
On a sunny day, dark asphalt absorbs solar radiation and gets far hotter than the surrounding air — commonly 40–60°F hotter at midday. A widely-cited measurement set, popularized by the American Kennel Club, illustrates it:
- Air 77°F on a sunny day → asphalt about 125°F
- Air 86°F → asphalt about 135°F
- Air 87°F → asphalt about 143°F in some measurements
At around 125°F, skin can sustain a burn in roughly 60 seconds. That's why a walk that feels fine to you can still injure your dog's paw pads.
The model
We compute:
surface_temp = air_temp + solar_gain
The solar gain is driven primarily by shortwave (global horizontal) solar radiation, which already reflects how much cloud is blocking the sun, with small corrections for cloud cover, recent rain, and night-time residual heat:
- Full midday sun adds roughly +45–55°F on dark asphalt, calibrated so the anchor points above are reproduced within a few degrees.
- Overcast skies cut the gain to about +10–20°F, because far less solar energy reaches the ground.
- Night keeps only a small residual (up to ~+5°F right after sunset), decaying to zero within about two hours as the slab radiates its stored heat away.
- Recent raincaps the gain at +10°F — wet pavement can't run hot while it's evaporating.
We also compute the heat index(the NWS "feels-like" temperature) from air temperature and humidity, because humid heat stresses dogs even where pavement isn't the limiting factor.
Safety thresholds
The estimated pavement temperature maps to a verdict:
| Dog type | SAFE | CAUTION | DANGER |
|---|---|---|---|
| Normal (most adult dogs) | below 110°F | 110–125°F | above 125°F |
| Flat-faced, senior & puppy | below 105°F | 105–120°F | above 120°F |
Regardless of pavement temperature, we force at least CAUTION whenever the heat index climbs above 90°F, to account for humidity-driven heat stress.
Where the data comes from
- Live weather: Open-Meteo — hourly air temperature, shortwave radiation, cloud cover, precipitation, humidity, and day/night. Free, no API key. Live checks update at least every 30 minutes.
- Monthly "typical" notes:derived from Open-Meteo's ERA5 historical archive (recent-years averages), run through the same model to estimate a typical safe window per month.
- City & postal locations: GeoNames (CC BY 4.0).
Honest limitations
This is a model, not a thermometer on your street. Real pavement temperature varies with surface color and material (fresh asphalt vs. weathered concrete), shade, wind, and how long the sun has been on it. Treat our verdict as a strong prompt to check for yourself. The definitive test is free and takes seven seconds: press the back of your hand to the pavement — if you can't hold it comfortably, neither can your dog.