The dramatic drop in temperatures unleashed violent weather across much of the state of North Rhine-Westphalia.
A 54-year-old woman on a scooter died in Cologne after she sought shelter from the wind and rain under an underpass and was hit by a truck. A 47-year-old woman in Nordhorn in Lower Saxony also died after gusty winds uprooted a tree that fell on her as she tried to return home with her dog.
A 15-year-old girl suffered life-threatening injures after she was struck by falling branch while riding a bike in Wesel county. Winds in Bonn tore down a 2.5-metre-high wooden fence in the city centre, injuring six people. A 62-year-old woman suffered serious injuries.
The strong winds also caused a tornado on the North Sea island of Helgoland, where eight people were injured, two seriously. The twister tore across a camping site, leaving more than 100 people without a place to sleep tonight. The island's mayor called a state of emergency and asked for help from the mainland.
The storm front hitting western Germany on Monday afternoon is expected to bring heavy rain, hail, strong gusting winds and even the danger of isolated tornadoes as it sweeps across the country, the DWD said.
The deadly storm will also cause the high temperatures of recent days to drop markedly, with the west to see overnight lows to fall to 17 degrees Celsius compared to average lows of 22 degrees overnight in the east.
The DWD warned any respite would be short-lived however, with high temperatures set to drop only a little Tuesday, to between 25 and 30 degrees Celsius. The east of the country could expect thunderstorms on Tuesday, the office added.
The baking summer conditions could return Wednesday with temperatures of more than 30 degrees being felt across the country. Only the coastal areas and islands off the coast could expect cooler temps, with highs around 25 degrees and upwards. Southern Germany is set to swelter amid highs of about 36 degrees.