Thunderstorm warnings are only issued for categories 3 and 4. In spite of the most up-to-date tools and methods, it is not currently possible to predict or give several hours’ warning of the strength, timing and location of severe thunderstorms. Three of the categories are therefore of little significance.
| Possible impacts |
|
|---|---|
| Description of measurement and prognostic values | Very severe thunderstorm (flash storm, localised; warning time 0 to 1 hour): >120 km/h, >4 cm hailstones, >50 mm/h |
| Possible impacts |
|
|---|---|
| Description of measurement and prognostic values | Severe thunderstorm (flash thunderstorm; localised, warning time 0 to 1 hour): 90-120 km/h, 2-4 cm hailstones, 30-50 mm/h |
A thunderstorm event that is usual for the time of year (for which, therefore, no special warnings are issued).
What to do during a thunderstorm
When widespread severe thunderstorms could potentially occur, a "Widespread (very) severe thunderstorm possible" warning is issued (hatched area on the hazard map).
Thunderstorms can develop very quickly and it is impossible to accurately predict their strength, timing or location several hours in advance. Only when a thunderstorm is present are localised thunderstorm warnings issued at short notice (up to one hour in advance).