Largest hail, last hour
Hail track
Latest
The largest hail of the last hour at each place, in inches across: the path each hail storm has cut.
.255 in
Storm analysis / Largest hail now
Hail size, live radar analysis
Over Pond at Hwy 151 and Reiner Rd at Madison, Wisconsin, where the map opens. The whole country
The largest hail each storm is holding now, in inches across, every ten minutes: which storms carry hail, and how large. How to read it.
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 hail size map shows
The largest hailstone each storm is likely holding now, in inches across, worked out from how strong the storm’s echo is and how high above the freezing level it reaches. Half an inch is a pea or a marble; 1 inch, a quarter, is severe; 1.75 inches is a golf ball, 2.75 a baseball.
How to read it
- Under 0.75 in
- Small hail, pea to marble.
- 0.75 to 1 in
- Penny to quarter; damage to plants.
- 1 to 1.75 in
- Severe: quarter to golf ball, dents in cars.
- 1.75 to 2.75 in
- Golf ball to baseball; broken windows and roofs.
- Over 2.75 in
- Giant hail, dangerous to people and animals in the open.
What it is for
- See which storm will bring hail before it arrives, and how large.
- Get cars and people under cover in time.
- Read with the hail track to see where a storm has already dropped hail.
How it is made
The storm analysis joins every radar in the national network every two minutes into one picture of the country on a grid about two thirds of a mile across, cleaned of ground clutter, birds and insects, and measures from it what no single radar shows: the largest hail, the turning of the wind, how high a storm’s heavy echo reaches above the freezing level, and what is falling, read with the temperature of the air. Storm Station keeps it every ten minutes for a day, the gauged rain and the radars’ view each hour, and draws it at every zoom from the analysis’s own grid.
A frame every 10 minutes, played as a loop of 1 to 24 hours. As data: /radar/now.json?show=mesh, the times of its frames.
In the Field Book
- SupercellFB-EVT-007
- ThunderstormFB-EVT-001
Over a state
AlabamaAlaskaArizonaArkansasCaliforniaColoradoConnecticutDelawareDistrict of ColumbiaFloridaGeorgiaHawaiiIdahoIllinoisIndianaIowaKansasKentuckyLouisianaMaineMarylandMassachusettsMichiganMinnesotaMississippiMissouriMontanaNebraskaNevadaNew HampshireNew JerseyNew MexicoNew YorkNorth CarolinaNorth DakotaOhioOklahomaOregonPennsylvaniaRhode IslandSouth CarolinaSouth DakotaTennesseeTexasUtahVermontVirginiaWashingtonWest VirginiaWisconsinWyoming
With it
Severe AlertsWeather by stateForecast accuracyInstrument atlas
Beside it
Heavy echo above freezing
Hail core
Latest
How far above the freezing level each storm holds its heaviest echo, in thousands of feet: the taller the core, the larger the hail it can grow.
035,000 ft
Echo tops
Storm tops
Latest
How tall each storm stands, in feet: the higher the top, the stronger the storm and the more likely hail and wind.
560,000 ft