In the years after the subsidy era ended, few people owned air conditioners. Even during power outages, a few minutes with a bamboo hand fan was usually enough to fall asleep.
Since the 2000s, both the climate and the city have changed rapidly. Summers today can turn much of the country into a furnace. Hanoi ranks among the hottest cities, with some days approaching 41 degrees Celsius while nighttime temperatures linger at 28-30 C.
The city is not only getting hotter. It is also losing its ability to cool itself after sunset.
Many parts of the world are facing similar heat shocks. South Asia has seen temperatures of 45-46 C. Central Europe endured an unusually hot May, with temperatures climbing above 35 C.
Two layers of causes are at work.
