By Robert Greenall, BBC News
Much of southern Europe is baking in extreme heat, with Greece seeing temperatures of 40C or more.
The Acropolis, the country's most popular tourist attraction, was closed during the hottest hours of the day to protect visitors.
Potentially record temperatures are expected next week as another heatwave approaches.
The European Space Agency (ESA) says Italy, Spain, France, Germany and Poland may see extreme conditions.
The ESA monitors land and sea temperatures via its satellites.
The hottest temperature ever recorded in Europe was 48.8C in Sicily in August 2021.
There are also fears in Greece of a greater risk of wildfires, especially in areas with high winds. It suffered major wildfires in 2021 in another exceptional heatwave.
In Croatia, fires broke out on Thursday, burning houses and cars in at least one village, Grebastica, on the Dalmatian coast. Officials told Croatian TV on Friday morning that the fire had been brought under control.
High temperatures have also been reaching into central parts of Europe, with Germany and Poland among countries affected.
Czechia's meteorological office issued a warning that temperatures at the weekend could go above 38C, which is exceptionally high for the country.
Meanwhile in the UK, heavy showers and gusty winds are expected in parts of England on Saturday.
Meteorologists quoted by PA suggested this was because the southern shift of the jet stream which was fuelling the hot weather in Europe, was also drawing low-pressure systems into the UK, bringing unsettled and cooler weather.
Earlier this week, a man in his forties died from the heat after collapsing in northern Italy - while several visitors to the country have collapsed from heatstroke, including a British man outside the Colosseum in Rome.
The cause is the Cerberus heatwave - named by the Italian Meteorological Society after the three-headed monster that features in Dante's Inferno.
Italian weather forecasters are warning that the next heatwave - dubbed Charon after the ferryman who delivered souls into the underworld in Greek mythology - will push temperatures back up above 40C next week.
Heatwaves are also being seen in parts of the US, China, North Africa and Japan.
Greece's Culture Ministry announced the closure of the Acropolis on Friday from 12.00 to 17.00 (local time), saying similar measures were likely to follow on Saturday.
Temperatures were expected to peak at 41C in central Athens on Friday, but the Acropolis sits on a rocky hilltop and is usually hotter.
There is little shade on the hill for respite.
Earlier on Friday at least one tourist was stretchered out of the site after falling ill due to the heat, local police said.
Several other tourist sites around the Sacred Rock where the Acropolis stands remained open throughout the day.
In recent days the Greek Red Cross has been deployed to provide water bottles and help people feeling nauseous and dizzy in the heat.
People have been advised to drink at least two litres of water a day and to avoid coffee and alcohol, which are dehydrating.
Last month was the hottest June on record, according to the EU's climate monitoring service Copernicus.
Extreme weather resulting from warming climate is "unfortunately becoming the new normal", the World Meteorological Organisation (WMO) has warned.
Periods of intense heat occur within natural weather patterns, but globally they are becoming more frequent, more intense and are lasting longer due to global warming.
- This story was first published on the BBC