Slow-down by temperature and dew point
| Temperature | Dew 8°C | Dew 13°C | Dew 18°C | Dew 22°C |
|---|---|---|---|---|
| 10°C (50°F) | 0% | |||
| 15°C (59°F) | 0.3% | 0.7% | ||
| 18°C (64°F) | 0.6% | 1.0% | 1.9% | |
| 21°C (70°F) | 0.8% | 1.5% | 2.4% | |
| 24°C (75°F) | 1.2% | 2.1% | 3.0% | 4.1% |
| 27°C (81°F) | 1.7% | 2.6% | 3.8% | 4.8% |
| 30°C (86°F) | 2.2% | 3.2% | 4.5% | 5.7% |
| 33°C (91°F) | 2.8% | 4.1% | 5.4% | 6.6% |
How it works
Add the air temperature and the dew point, both in Fahrenheit. Up to 100 there's no change. From there the slow-down climbs: about 1% at 120, 3% at 140, 6% at 160 and 10% at 180. Above 180, hard running is not advised. We fill in between the steps in a straight line. This is coach Mark Hadley's table.
Heat costs more on long efforts than short ones, so for a marathon err towards the slower side. Adjust by effort and heart rate as well: if your easy runs feel hard, they are hard. The forecast comes from Open-Meteo; your location is only used to fetch it.
Racing soon? Set your pace band to the adjusted finish time, and plan your drinks with the fuelling calculator.