The mayor of the island of Kimolos warned the island was without water and the situation was unlikely to improve any time soon.
"We need help. There has been no water on the island since yesterday," Mayor Theodoros Maganiotis told state TV.
Locals and tourists in the Cyclades have complained of lengthy cuts in water supply after a year-long drought. Greece, along with other parts of southern Europe have been hit by a heatwave over the last week with temperatures reaching up to 46 degrees Celsius.
In Athens alone, where nearly half the Greek population lives, water reserves have fallen by 26.4 per cent in July from the same month last year, the capital's water company EYDAP said.