The deaths came as the overwhelmingly Muslim country of around 200 million people observes the Islamic month of Ramadan, during which eating and drinking is forbidden from sunrise to sunset.
Some clerics have issued public warnings saying that physically weak people can abstain from fasting in these tough conditions.
The provincial government meanwhile announced a public holiday to encourage residents to stay inside, an official said.
Prime Minister Nawaz Sharif has issued special instructions to the National Disaster Management Authority and other relevant organisations to arrange urgent assistance for the heat wave victims.
Al Jazeera's Kamal Hyder, reporting from Islamabad, said most of the victims elderly and poor, many of them living in the streets.