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Blue through red: how hard it is raining, not what kind of weather it is.
Also known as: Rain radar, Coloured blobs on a rain map
A colour ramp showing radar reflectivity, which is a proxy for rainfall rate. Green is light, yellow moderate, red heavy — and the scale is set by whoever made the map, so two apps can colour the same rain differently.
A colour scale on a radar image representing reflectivity, which stands in for precipitation rate: blues and greens for light rain, yellows and oranges for moderate, reds and purples for heavy.
Contexts: Maps
The scale is a presentation choice rather than a standard, so the same rainfall appears in different colours on different services and the key must be read before the colours mean anything.
Red on one app can be the same rainfall as orange on another.
Radar measures what reflects, not what reaches the ground. Hail returns strongly and can colour as extreme rainfall, and precipitation that evaporates before landing shows on the image and never falls.
Irregular curved patches of colour over a map, graded from pale blue through green and yellow to red, beside a rectangular colour key.