Large parts of northern and central India are bracing for more days of brutal heat, with temperatures forecast to hit 50°C this week. Hotter than the searing 43°C heat on Thursday that scorched New Delhi, the capital city, while a teacher, Shyam Mahato, struggled to keep pupils safe and hydrated from his school’s single tap.

“Heat is getting worse much earlier,” says Mahato, whose classroom is an exposed space underneath a bridge without air conditioning or even a fan.

Blazing temperatures have made it a constant daily struggle for people enduring this long-running wave of severe heat. Aside from a few days of respite, extreme heat has afflicted a region with more than a billion people since March. That’s when temperatures in India broke a 122-year record. Neighbouring Pakistan has already experienced 50°C...