Rescuers in central Greece are trying to reach hundreds of people trapped by floods that have left villages submerged and 10 people dead.
Prime Minister Kyriakos Mitsotakis said Greeks face a “very unequal battle” with nature.
Rivers burst their banks, while homes and bridges were swept away after days of heavy rain.
Residents in villages around Palamas and Karditsa appealed for food and water.
After weeks of scorching temperatures and forest fires, the plains of Thessaly were flooded by a three-day storm.
Up to 800 mm (31.5 in) of rain fell in 24 hours – more than a year’s rain – flooding the flat terrain in central Greece.
The latest city to be threatened is Larissa, home to 150,000 people, where the Pineios River burst its banks in some suburbs.
It is one of the largest cities in Greece and the agricultural center for the whole country. But almost a quarter of this year’s crop was lost.
It will take years for the land to be fertile again. Where the water receded, a thick layer of mud was left behind.
Satellite images showed that almost 73,000 square meters of land in Thessaly had been flooded.
Many people in the region are furious with the Greek authorities. They accuse ministers of using climate change as an excuse for bad construction projects.
One bridge collapsed due to a cyclone three years ago, so they rebuilt it. Now it is completely destroyed again. Many Greeks see this as a symbol of government failure.
The city of Larissa is unrecognizable. Many roads are very steep. The houses at the bottom of the road are now completely flooded, while the houses at the top are intact – for now.
The damage to infrastructure is enormous. Many roads are impassable and bridges destroyed due to the ferocity of the storm.
But at the same time there are also burnt trees and scorched earth – debris from the devastating forests that Greece has been fighting against all summer.
Xenia, a 50-year-old woman with thick curly hair, holds back tears as she looks at her house from afar – only its yellow roof is visible. She has lived there for over 30 years with her family.
“I never believed this could happen. Right now, there is about one and a half meters of water in my house,” she told the BBC.
“It is completely destroyed and I have nothing left, just my job, this house and my children.
“Tonight I will be hosted by a colleague, maybe even longer. My children will sleep with friends whose houses are safe. I may never return to this house, where I have unfortunately lived all my life, and rented a cheap apartment. that I can to pay with my low salary.”
The death toll has risen to 10 and at least four people are missing, according to the Greek civil protection minister, Vassilis Kikilias. There are fears that it could increase further as rescuers can reach more of the flooded areas.
Visiting some of the most affected areas, the Greek prime minister said the country was dealing with “a natural phenomenon we have never seen before”.
Mr Mitsotakis promised to compensate people whose houses were destroyed or damaged as quickly as possible.
“We will do everything humanly possible. I understand both anger and rage. I have never hidden, I am always here in difficult times,” he said.
The rain has now largely stopped, but the flood waters in some areas are in places greater than 2m (6.5ft) deep.
The coastal town of Volos has been without clean drinking water for four days. Residents were seen collecting water from fountains and the sea with buckets and barrels, reports said.
The Greek fire brigade said more than 1,800 people had been rescued across Greece since Tuesday.
It said it continued to search for several missing people, including an An Austrian couple swept away with the holiday home they spent their honeymoon inside.
The flood follows Greece’s hottest summer on record and massive forest fires in the north of the country.
Scientists say extreme weather events are becoming more frequent and more intense as a result of climate change.