Around 40 people in France, mostly elderly, have died in a heatwave over the past week and Czech energy grid operator CEPS announced a state of emergency after its power network was overloaded.

Blackouts forced some Czech firms to trim operations and conserve power and CEZ, Europe’s second largest electricity exporter, said it had stopped exports for two days to boost local supplies after several generators failed.

The heatwave has boosted power demand across Europe as consumers turn up their air conditioners. Meteo France, the national weather agency, has put its heatwave alert at orange, the second highest level, in 53 of the 96 metropolitan departments, or administrative districts.

A top French health advisory body (INVS) said it would publish today a detailed toll from the heatwave which has so far proved less deadly than the 2003 hot spell which killed some 15,000 people.

Dutch meteorologists say they cannot make a direct link between global warming and the heatwave in Europe although the KNMI has forecast a clear warming trend over the next 50 years and increasingly frequent heatwaves.

While consumption has increased as millions of Europeans try to keep cool, electricity production in Europe has dropped because power stations face cooling problems. Spain’s oldest nuclear power plant has been forced to shut after river water got too hot to cool the reactor.