Italy limited work outdoors, France shut schools and Turkey battled wildfires on Tuesday in a European heatwave that meteorologists said was "exceptional" for striking so early this year.

Spain confirmed its hottest June on record, while temperatures passed 40 degrees Celsius in some of its cities on Tuesday.

Likewise, heat scaled to reach 40 degrees in the Italian city of Trento, while northern European cities such as London were also sweltering.

Europe is heating up at twice the global average speed and is the world's fastest-warming continent, the European Union's Copernicus Climate Change Service has said.

"What is exceptional ... but not unprecedented is the time of year," said World Meteorological Organization spokesperson Clare Nullis.

Europe was experiencing extreme heat episodes "which normally we would see later on in the summer," she said.

Some countries issued health alerts and trade unions attributed the death of a construction worker near the Italian city of Bologna on Monday to the heat.

Outdoor work was banned in some Italian regions during the hottest hours of the day as Italy issued heatwave red alerts for 17 cities, including Milan and Rome.

Power outages, likely caused or aggravated by spiking electricity consumption from air conditioners, were reported in central Florence and in the northern city of Bergamo.

In Sicily, a woman with a heart condition died while walking in the city of Bagheria, news agencies reported.

In the Spanish city of Barcelona, authorities were looking into whether the death of a street sweeper at the weekend was heat-related.

The Red Cross set up an air-conditioned "climate refuge" for residents in Malaga in southern Spain, said a spokesperson for the International Federation of Red Cross and Red Crescent Societies.

Turkey continued to battle the wildfires that forced the temporary evacuation of around 50,000 people on Monday in areas surrounding the city of Izmir and in the nearby province of Manisa, as well as Hatay in the southeast.

In France, nearly 1,900 schools were closed, up from around 200 on Monday.

Scientists say greenhouse gas emissions from burning fossil fuels are a cause of climate change, with deforestation and industrial practices being other contributing factors. Last year was the planet's hottest on record. (Reuters)