Heatwave upends Fourth of July events across US, strains power grids

A dangerous heatwave upended Fourth of July celebrations across swathes of the central and eastern United States on Friday, forcing officials in the nation’s capital and elsewhere to cancel or postpone dozens of parades, concerts and fireworks displays.

Among the events disrupted by the sweltering heat was the Great American State Fair on the National Mall in Washington, a centrepiece of President Donald ‌Trump’s efforts to mark the nation’s 250th birthday.

The fair, designed to showcase all 50 states, was temporarily closed on Friday afternoon as temperatures reached 38 degrees Celsius (101 degrees Fahrenheit).

Late on Friday, organisers of the National Park Service’s Independence Day Parade in Washington announced they had cancelled the annual event due to safety concerns. The parade had been scheduled to start at 10.30am local time on Saturday, with the Weather Service projecting heat index values to reach as high as 46 degrees.

Record-breaking temperatures spread to the eastern US from the Midwest earlier this week due to the emergence of a high-pressure system known as a “heat ⁠dome”, which traps a mass of hot air over a region and can cause humidity to spike.

The scorching conditions also strained power grids. PJM, the largest US power ‌grid operator serving 67 million people in the mid-Atlantic, South and Washington areas, ordered customers enrolled in emergency conservation programmes to curb usage. The steps were needed to battle generator outages, overloaded transmission lines and a surge in air-conditioning demand due to the heat.