A marine heat wave in the Mediterranean is combining with a powerful heat dome to cause Europe to swelter under a brutal early summer heat wave.

Punishing temperatures were forecast to reach 40 degrees Celsius (104 degrees Fahrenheit) in Paris and to stay unusually high in Belgium and the Netherlands. In contrast, temperatures were falling in Portugal, where no red heat warnings were issued.

Schools were partially shut in France, iconic monuments closed to tourists, and cities across Europe put on high alert as a record-breaking early summer heatwave spread across the continent Tuesday.Withering conditions that have baked southern Europe for days crept northward where such extremes are much rarer,

A heat dome hovered over France, Portugal and Spain to Turkey, while data from European forecasters suggested other countries were set to broil further in coming days.