Severe Heatwave Grips Large Parts of US as Triple-Digit Temperatures Spread Across Country

A severe heatwave spread across large parts of the United States on Saturday, with forecasters warning that temperatures could climb into the triple digits across the Southwest and Great Plains and persist for more than a week.

Meteorologists said a strong dome of high pressure was trapping hot air over much of the country, allowing the heatwave to expand eastward. The system is expected to affect as much as two-thirds of the continental United States.

Earlier this month, the National Weather Service (NWS) placed nearly 120 million people under extreme heat warnings. Forecasts indicated temperatures ranging from 32°C to 40°C, with high humidity pushing the heat index to around 46°C in some areas.

The NWS warned that temperatures in parts of North Dakota would exceed 100°F (37°C) through Tuesday and urged residents to stay hydrated and seek shelter, as temperatures in several regions were expected to remain 8°C to 14°C above average, even overnight.

In St. Paul, volunteers distributed frozen towels, washcloths, battery-powered fans, water, food and hygiene supplies to people living in encampments, while residents heading to cooling centres were seen using ice packs to cope with the heat.

The National Weather Service forecast that more than 90 local temperature records could be tied or broken by Wednesday, with about two-thirds involving unusually warm overnight temperatures.

Night-time temperatures were expected to remain above 80°F (27°C) in Fort Lauderdale, Miami and Tampa in Florida, as well as Galveston, Texas, and Charleston, South Carolina.

Record triple-digit temperatures were also forecast across Nevada, Utah, Colorado, Wyoming, Idaho, Montana and the Dakotas. Temperatures in Helena, Montana, were expected to reach 95°F (35°C), while parts of Nevada could see highs of 111°F (44°C).

Meteorologists warned that the heatwave could heighten wildfire risks in already dry regions, including parts of the Rocky Mountains.

The heatwave has been driven by a heat dome, a weather pattern in which a high-pressure system traps hot air while preventing cooler air and rainfall from entering the region. Chad Merrill, a senior meteorologist with AccuWeather, said it was one of the strongest heat domes to affect the Dakotas in 25 years.

Scientists say human-driven climate change is increasing the frequency, intensity and duration of heatwaves by warming the planet through greenhouse gas emissions from fossil fuels.

Weather patterns this year are also being influenced by El Niño, the periodic warming of the equatorial Pacific Ocean that can contribute to higher global temperatures. According to the U.S. National Oceanic and Atmospheric Administration, there is an 81% chance that El Niño will strengthen into a "very strong" event by the autumn of 2026.

(inputs from AP)