Heat and humidity make the pace you're running more effortful. Dew point (not humidity %) is what determines whether sweat can evaporate and cool you down. Enter the heat conditions and your typical pace, and get the pace that delivers the same effort and therefore the same training effect.
or
Auto-fill today's conditions, or set the sliders yourself.
78°F
65°F
Dew point is typically best as it barely changes throughout the day. Find it in any weather app.
Format m:ss — e.g. 8:30
Run today at
9:14 / mi
+2.5% +14 sec / mi
Heat stress score143
≤100 no adjustment140180+ don't run hard
Reference chart (temp + dew point, °F)
Combined score
Pace adjustment
Reads as
Based on the temperature + dew point adjustment chart popularized by coach Mark Hadley. Adjustments are interpolated within each band and are estimates — heat tolerance, acclimation, sun exposure, and run duration all shift the real number. Use effort as the final judge. Location lookups go straight from your browser to the National Weather Service (weather.gov) and are never stored.
