The water supply to residents of the Turkish capital Ankara has been reduced to two days on, two days off because of a severe drought.
The temperature has reached a sizzling 43C in Istanbul
The water level in reservoirs supplying the city has dropped to less than 5% of capacity, as the country suffers one of its driest years on record.
Snowfall in the winter was much lower than normal.
Municipal staff are to be sent on a two-month holiday to ease demand. About four million people live in the city.
Istanbul's mayor has said he has no plans yet to impose similar water cuts.
Television broadcasts and sermons in mosques have urged people to cut water consumption, the Associated Press reports.