where it comes from
The history is ERA5, the reanalysis made by the European Centre for Medium-Range Weather Forecasts for the Copernicus Climate Change Service. It rebuilds every hour since 1940 from stations, balloons, ships and satellites.
It is served, free and open, by Open-Meteo. The radar is a mosaic of national weather radars gathered by RainViewer, on a map from OpenStreetMap and CARTO. Places come from GeoNames.
how to read it
Each dot is one hour, day, week, month or year. Colours stretch across each place’s own range, so a deep orange in Fairbanks is not the same heat as one in Houston. Hover or tap a dot for its number.
The radar view shows only rain, whatever measure you pick, and only where countries share their radar: most of North America, Europe, Japan and Australia, and parts of elsewhere.
A reanalysis describes a patch of sky about 25 km across, so a dot is the weather of a neighbourhood, not of one thermometer. The newest five days are still being checked and are left out.