Warning levels and criteria at "Wettergefahren-Frühwarnung" - Overview:
Parameter Alert Level 1 Alert Level 2 Alert Level 3 Alert Level 4
Maximum Wind gusts > 75 kph > 90 kph > 105 kph > 120 kph
Daily Maximum Temperature > 30°C > 35°C > 40°C > 45°C
Daily Minimum Temperature < -15°C < -20°C < -25°C < -30°C
Convection (SWEAT-Index) > 150 > 250 > 350 > 450
Sultriness (Vapor Pressure) > 19 hPa > 23 hPa > 27 hPa > 31 hPa
Precipitation (3h) > 10 mm > 20 mm > 30 mm > 40 mm
Precipitation (6h) > 30 mm > 40 mm > 50 mm > 60 mm
Precipitation (12h) > 50 mm > 60 mm > 70 mm > 80 mm
Precipitation (24h) > 60 mm > 70 mm > 80 mm > 90 mm
Precipitation (Day 1-2, 48h) > 80 mm > 100 mm > 120 mm > 140 mm
Precipitation (Day 1-3, 72h) > 100 mm > 150 mm > 200 mm > 250 mm
Precipitation (Day 1-4, 96h) > 150 mm > 200 mm > 250 mm > 300 mm
Snow Accumulation (24h) > 10 cm > 15 cm > 20 cm > 25 cm
Black Ice (24h) One Alert Level yes

Symbol Event Description
Heavy rain Precipitation event with abundant, long lasting and mostly widespread rain. Flooding, At least some creeks and rivers in flood stage. In mountainous terrain landslides and mudflows.
Heavy rain and
heavy snow
Precipitation event with abundant, extensive rain in low lying areas with danger of flooding. At higher elevations long lasting and heavy snowfall accompanied by disruptions due to snow, ice, snow-breakage and snow drift.
Heavy snowfall Precipitation event with long lasting snowfall. Massive snow accumulation even in lowlands. Disruption and danger due to snow, snow breakage and snow drift.
Icing Precipitation event with rain across a larger area at air temperatures below zero and/or surface temperatures below zero. Rain amounts can be only marginal. Danger due to black ice and/or ice breakings.
Tropical cyclones Tropical systems (tropical storms, tropical cyclones, e.g. hurricanes, typhoons) of the subtropics if threatening inhabited areas (islands or mainlands). Hazards: Flooding, landslides, storm surge, wind
Extratropical storms Strong extratropical low pressure systems, developing in the westerlies of both hemispheres, when affecting inhabited areas (islands or mainland). Lows are associated with large scale strong wind or gale that make wide spread damage likely. Wind may cause severe storm surge. Local wind systems with extreme wind speeds might also be triggered (Föhn, Bora, Mistral).
Thunderstorms, hail Small scale and short time heavy rain events. My be accompanied by lightning, hail, storm force wind gusts. Danger of local flash floods, hailstorms, and extreme wind speeds. Konvektives, kleinräumiges und kurzzeitiges
Tornadoes Extreme wind speeds along a path of several km or several hundred km in length and 10 to 1000 meters wide. In association with strong thunderstorms. Tornadoes may cause complete destruction of buildings and infrastructure.
Heat waves Very unusual or extreme high temperatures depending on elevation, latitude and season.
Cold spells Very unusual or extreme low temperatures depending on elevation, latitude and season. Damage due to frost, ice drift.
Flooding Large scale flooding due to widespread long lasting or repeated intense rain events (e.g. monsoon). Even large rivers are on flood stage. Flooding may be enhanced by a strong thaw period.
Drought Very low soil moisture in areas with absence of rainy season or when onset of rainy season is much too late. In otherwise humid areas, when lack of rain persists over months. Major losses in agricultural sector, shipping. Drinking water supply at risk.
Wildfires, forest fires Wildfire or bushfires that are caused by heat, drought, lightning or arson. Fires may burn for weeks or months and destroy areas of more than 1000 km² including houses, villages and infrastructure.