Washington: The extreme weather disrupted power grids, sent electricity prices soaring and affected Independence Day celebrations across the country, including in Washington, D.C., where severe conditions led to the cancellation of a parade and significant delays to the president’s speech.

The National Weather Service had warned nearly 130 million people of a “long and dangerous heat wave” affecting the Ohio Valley, south-central United States and the East Coast. The intense heat, driven by a heat dome, was followed by severe thunderstorms on Saturday as high humidity added to the instability in the atmosphere.

By Sunday evening, outages were reported across more than 12 states. According to PowerOutage.com, around 220,000 homes in Michigan, 180,000 in Pennsylvania and 120,000 in New Jersey were without power. More than 100,000 people in New York also faced outages.

The combination of intense heat and humidity pushed temperatures to 40.5 degrees Celsius in some East Coast cities and parts of the Southwest. While conditions began easing by Sunday evening, the National Weather Service warned that clusters of severe thunderstorms could continue to bring widespread strong winds.

The Financial Times reported that electricity prices rose sharply across the eastern US as demand surged and storms disrupted supply networks. Wholesale spot electricity prices jumped by more than 240 per cent in New England, doubled in New York City and increased by more than 50 per cent in the American Midwest, based on figures from the Energy Information Administration.

In Washington, D.C., temperatures were forecast to reach 36 degrees Celsius as authorities continued to deal with the impact of the severe weather across the region.