Weather at your pace
The weather cost, heat stress, why the route is coloured and where the forecast comes from.
- What does the weather cost mean?It’s how much longer the weather will make your run at your pace than it would take in ideal conditions, for example “+3 min 25 s”. RunFast adds it up stretch by stretch from the heat and humidity, the cold and the wind at the hour you’ll reach each one. Under 30 seconds, it says Ideal.
- What do the heat stress levels mean?RunFast grades heat stress by WBGT, one number for the air, humidity, sun and wind, the reading race medical teams set their flags by. Low is under 18.3 °C (65 °F), Moderate from 18.3 °C (65 °F), High from 22.8 °C (73 °F) and Extreme from 27.8 °C (82 °F).
- Why is my route coloured green, yellow, orange and red?The colour shows how much the weather slows you on each stretch at your pace. Green is Ideal, yellow A little slower (1% or more), orange Hard (3% or more) and red Very hard (6% or more). It counts the heat and humidity, the cold and the wind at the hour you’ll be there.
- Where does RunFast’s forecast come from?From Apple Weather: RunFast asks it for the weather at points along your route, for the hour you’ll reach each one at your pace, then works out the heat stress, feels like, dew point and weather cost itself. RunFast’s numbers are worked out from Apple Weather’s. Past race days come from Copernicus ERA5.
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