The storm has already claimed several lives, while more people remain missing.
Heavy rainfall has triggered landslides, destroyed buildings, and carried away dozens of cars.
Aerial footage shows roads completely washed out by muddy water, and bridges wiped out by swollen rivers.
"We have never experienced anything like this before in all these years," says this woman, adding, "The water was too much."
Prime Minister Kyriakos Mitsotakis postponed an annual economic speech scheduled for this weekend.
He is planning a visit to the affected areas in the coming days.
It all comes just days after a two-week deadly wildfire died out in the north.
One described by authorities as the most extreme on record.
Hannah Cloke is a professor at Reading University.
"We've got climate change right here in our hands. We can see it in these hot temperatures that we've been experiencing, we've seen heat waves, but also marine heatwaves so the ocean has been very, very warm. And of course, all the extremes that come along with that and more energy in the system, so devastating wildfires, intense rainfall as well."
Since Tuesday, more than 800 people have been evacuated across the country, most of them in the Thessaly region.
Rescue workers are now searching for those who stayed behind.
