BERLIN: A heatwave sweeping Europe was starting to peak in Germany on Thursday, with several open-air events canceled and temperatures expected to top 40C through the weekend.

Large parts of the country are already under “severe to extreme heat stress” with temperatures soaring to around 37C, the German Weather Service (DWD) said.

In an unprecedented step, rail operator Deutsche Bahn warned customers to avoid travel and said it would refund any tickets booked up to June 30 due to a high risk of disruption from wildfires, heavy summer rain and thunderstorms.

Several open-air sports events have been canceled, including a half-marathon in Hamburg where authorities cited the risk of “an increased demand for emergency and rescue services.”

The mercury will rise further in Germany starting Friday and on Saturday, when almost the entire country is forecast to bake under temperatures of 35 to 41C.