Citizens in areas around Volos and Lamia have been told to move to safety as the country remains in the grip of a severe heatwave.
Meanwhile, fires continue to rage on the islands of Rhodes, Corfu and Evia.
Greece is one of a number of countries currently grappling with wildfires, in which more than 40 people have died.
Kostas Agorastos, mayor of Greece's Thessaly region, which includes Volos, has accused "brainless workers" of starting the fire, according to the Ellada 24 news channel.
He added that it had broken out on four simultaneous fronts.