Severe thunderstorm warning

In the United States, the National Weather Service issues a warning when an observed thunderstorm is producing wind gusts of at least 58 miles per hour (93 km/h), or hail of at least 1 inch (2.5 cm) in diameter.

In the United States, the National Weather Service (NWS) defines a severe thunderstorm as having large hail of one inch (2.5 cm) in diameter or larger, surface wind speeds of 58 mph (50 kn; 93 km/h) or greater, and/or a tornado.

The product text will also provide a summary of impacts to life and property that may be caused by the hailstones and winds being produced by the parent thunderstorm.

When deemed necessary, initial warnings and Severe Weather Statement updates containing the "destructive" tag will be disseminated into the Wireless Emergency Alerts system as well.

[15] In Australia, a severe thunderstorm is defined as having damaging winds in excess of 90 km/h (49 kn; 56 mph), large hail of two centimetres (0.79 in) or larger, heavy rainfall, and flash flooding.

Severe thunderstorm warnings are issued by regional offices of the Bureau of Meteorology (BOM) based in Melbourne Docklands, Adelaide, Darwin, Perth and Brisbane.

[16][17] In New Zealand, a severe thunderstorm is defined by the Meteorological Service of New Zealand (MetService) (Māori: Te Ratonga Tirorangi) as having large hail of 20 millimetres (2.0 cm; 0.79 in), damaging winds of 110 km/h (59 kn; 68 mph), rainfall rates of at least 25 millimetres (0.98 in) per hour and/or tornadoes producing winds above 116 km/h (63 kn; 72 mph) (rated F1 or stronger on the Fujita Scale).

[20] Warnings are disseminated to the public through terrestrial television and radio outlets,[21] online media, and via SMS messages through the National Disaster Risk Reduction and Management Council's Emergency Cell Broadcast System.

On August 16, 2019 at 1:31 a.m. MDT, the National Weather Service in Cheyenne, Wyoming incorporated the "emergency" wording into a Severe Thunderstorm Warning.

In this instance, the "severe thunderstorm emergency" statement was included to denote that three-inch (7.6 cm) diameter hail (as confirmed by storm spotter reports) was imminent in portions of Scotts Bluff, Banner and Sioux Counties in Nebraska, specifically areas around the towns of Scottsbluff and Gering.