AUTHORITIES across the northern hemisphere issued health warnings and advice on staying hydrated over the weekend as Europe, Asia and America baked in a record-breaking heatwave.

Athenian authorities closed the Acropolis as temperatures in the Greek capital reached 41°C, while heat alerts were issued by 15 Italian cities including Rome, Bologna and Florence. Rome is forecast to hit temperatures of 42°C on Tuesday.

The alerts advise people to avoid direct sunlight between 11am and 6pm. The Italian Red Cross warned that most people are unaware of the health risks posed by such high temperatures.