As southern Pakistan sears in temperatures hitting 45 degrees celcius health officials say more than 700 people have died over the past three days.
Most of the deaths have occured in Karachi.
The situation is not helped by frequent power cuts that render fans and air-conditioning redundant.
Hospitals are inundated.
Seemi Jamali is head of A&E at the Jinnah Medical Centre:“We normally see about 1,100 patients every 24 hours. At the moment we are seeing 1,800 everyday, which is a tremendously high figure.”
Pakistan is currently observing Ramadan, during which eating and drinking are forbidden between sunrise and sunset.
Islamic clerics have appeared on television to advise those at risk of heatstroke to abstain from fasting.
The insecure power supply has crippled the civic water system making clean drinking water difficult to get hold of.
Authorities have announced a public holiday to encourage people to remain in the shade.