As South Asia bakes under a blistering heat wave, life-or-death decisions arrive with the midday sun.

Abideen Khan and his 10-year-old son need every penny of the $3.50 a day they can make molding mud into bricks at a kiln under the open sky in Jacobabad, a city in southern Pakistan. But as temperatures have soared as high as 126 degrees Fahrenheit, or 52 degrees Celsius, in recent days, they have been forced to stop by 1 p.m., cutting their earnings in half.

“This isn’t heat,” said Mr. Khan, sweat dripping down his face and soaking through his worn clothes. “It’s a punishment, maybe from God.”

It is yet another brutal summer in the age of climate change, in a part of the world that is among the most vulnerable to its dire effects. And there is more suffering to come: The extreme heat that Pakistan and neighboring India have been experiencing will continue for days or weeks, forecasters say. Already, it has exacted a deadly toll.

In the northern Indian state of Bihar, officials said that at least 14 people had died from the heat. Reports from other states in India’s north indicate that the count could be considerably higher. In both India and Pakistan, hospitals have reported large numbers of heatstroke cases.