Extreme heat will bake America’s cities

By Aryn Braun

The monsoon is late again. Without the almost biblical rains, there is nothing to break the heat during a long stretch of days above 43°C (109°F). The pavement is scalding. Hospital wards are filling with burn victims. Even the cacti seem crispy. Many people venture out only in the early morning, before the sun rises. The rest of the time they take refuge in air-conditioned rooms: the invention that makes life in the desert possible.

This was the scene in Phoenix, Arizona in July 2023. But what if the demand for electricity to power those air-conditioners had stretched the grid to breaking point? A study published in Environmental Science and Technology, a journal, suggests that a five-day heatwave in Phoenix, with a blackout, could kill more than 13,000 people and send more than half of the city’s residents to hospital.