Where does RunFast’s forecast come from?
Updated
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.
Apple Weather, timed to your run
- RunFast takes points along your route, about one every 1.5 km (1 mile).
- It times your run at your pace, with the hills, so it knows when you’ll reach each point.
- It asks Apple Weather for the forecast at each point, for that hour.
That’s why the start of a long run can be cool and the finish hot: each stretch gets its own hour.
Forecasts reach 10 days ahead. See no forecast yet.
What RunFast works out itself
Heat stress (WBGT), feels like at running pace, the dew point, the weather cost, the route’s colours and your split times for the hills. RunFast’s numbers are worked out from Apple Weather’s.
At the foot of every run you’ll see when the forecast was updated, such as “Forecast updated 4 min ago”, with the Apple Weather mark and a link to Other data sources.
Past race days
The race-day history for the Comrades, Berlin, London and Boston comes from Copernicus ERA5: the weather on the course, hour by hour, on the day each race was run. It isn’t a thermometer reading at the start line. See race-day weather.
Why it can differ from your weather app
Your weather app shows your town, now or by the hour. RunFast shows each stretch of your route at the hour you’ll be there, and works out feels like for someone running, often in the sun. See feels like for runners.
Your route stays private
Map your run reads your route file in your browser. Only the points go to fetch the forecast, rounded to about 10 m (33 ft), and they aren’t linked to you. See what RunFast keeps.