Thousands of people have been evacuated from homes and hotels on the island of Rhodes, according to Greece’s fire service.
Private boats have joined the Greek coastguard in helping to pick up people from beaches on the east of the island.
Greek navy vessels are also reported to be heading to the area, which is popular with tourists.
Five helicopters and 173 firefighters are operating in the area, with three hotels in the Kiotari area reported to have been damaged by fire.
One British woman said she was evacuated from the hotel she was staying at with her sister and daughter, but was now stuck on a beach with hundreds of others in the severe heat.
Simon Wheatley another Briton said ash had begun falling onto his pizza when he was eating.
Travel company TUI said a small number of its hotels had been affected and it was relocating customers to alternative accommodation as a precaution.
Firefighters from Slovakia arrived on Rhodes on Saturday to help local teams battling the fires.
Part of the Slovak rescue team had moved to the coastal resorts to help evacuation efforts there, they said.
It could turn into Greece’s hottest July weekend in 50 years, one of the country’s top meteorologists has said.
Firefighters are continuing to battle dozens of wildfires across the country.
An area west of Athens is among the worst-hit areas, along with Laconia in the southern Peloponnese and the island of Rhodes.
People have been advised to stay home, and tourist sites – including Athens’ ancient Acropolis – will be shut during the hottest parts of the next two days.
Greece – like a number of other European countries – saw a prolonged spell of extreme heat earlier this month.
The latest heatwave comes at one of the busiest times for the country’s tourism industry.