Live radar / Rain total, 1 hour

Rain in the last hour, radar total

Over Citizen station EW1637, Colorado, where the map opens. The whole country

All the rain of the last hour, in inches: the quickest way to see where the downpours are falling now. How to read it.

Last hour on the map

The rings are the storms the radars detect, the larger ring a severe one; each line runs to where its storm will be in an hour if it keeps its present speed and heading. Rotation and hail are what the radars detect and the analysis measures, not warnings: the official watches and warnings in force are drawn on the map in their own colours and set out in full under Alerts.

What the last hour map shows

All the rain that fell in the last hour, in inches, totalled by the radar network. Snow counts as the water it melts to. The quickest way to see where a downpour is falling.

How to read it

Under 0.1 in: A passing shower.
0.1 to 0.5 in: Steady rain.
0.5 to 1 in: Heavy rain; water ponds on roads.
Over 1 in: Flash flooding possible, above all in cities and steep ground.

What it is for

Find the downpours that may flood streets in the next hour.
Follow a slow storm that keeps raining on the same place.
Compare with the rain rate: a total that keeps climbing means the rain is not moving on.

How it is made

The totals are added up from the radar’s own estimate of how hard it is raining, a new one every two minutes, corrected against the rain gauges that report through the hour. Snow counts as the water it melts to. Each frame of a loop is the total to its own hour, so the swaths of rain move as it plays.

A frame each hour, played as a loop of 6 hours to 3 days. As data: /radar/now.json?show=p1h, the times of its frames.