Pakistani health officials say more than 25 people died from heatstroke in the southern province of Sindh on June 30.
The total death toll from a heat wave in Sindh now stands at 1,256, provincial health officials said on July 1.
Most of the deaths were reported from the provincial capital, Karachi.
The provincial government says the devastating heat wave has affected some 100,000 people in Karachi since it struck Sindh on June 20 with temperatures reaching up to 45 degrees Celsius.
Officials were criticized by residents and opposition parties for not doing enough to tackle the crisis.
Local residents say prolonged electric power cuts have made the matters worse.
The deadly heat wave coincided with the holy Muslim month of Ramadan, when the country's Muslim majority observed a dawn-to-dusk fast.
With reporting by dawn.com and AP