Paris — Europe is in the middle of a life-threatening heat wave. Records fell like dominoes on Thursday in cities in France, Germany, Belgium, the Netherlands and Britain. It hit 100 degrees in London, 109 in Paris — the highest temperature ever recorded there. But the French capital is not built for it.

Iconic landmarks became water parks, anything to beat the heat. But this latest hot spell isn't all frolicking in the fountains.

The high heat has officials concerned about the stability of Notre Dame Cathedral, which almost burnt down in April. They worry the stones could become unstable leading to a collapse.

Thursday's record-breaking heat wave in Paris hit 109 degrees, delaying trains, leaving passengers stranded and even affecting the power grid. A nuclear plant in southern France shut down two reactors due to the heat.

People cool off and sunbathe at the Trocadero Fountains in Paris, on July 25, 2019 as a new heatwave hits the French capital. Getty

Paris prepared with temporary solutions, free water and mist machines to cool commuters' heels. This could turn into a permanent problem as heat waves become more frequent and severe, big cities like Paris struggle to cope.

Scientists call it the "urban heat island." Buildings and roads absorb the heat during the day, then release it at night like a radiator, becoming a new challenge for old Europe.

A meteorologist in Paris said because of climate change, the extreme heat could become the norm.