Heat dome set to trap extreme temperatures across two-thirds of the United States

A high-pressure “heat dome” is projected to dominate much of the continental United States, keeping temperatures well above normal for several days. Meteorologists say the ridge could trap hot air for a week or longer, producing triple-digit highs in the Southwest and Great Plains this weekend before moving eastward.

The National Weather Service warns that many areas will see temperatures 15 to 25°F (8 to 14°C) hotter than average, including overnight readings that may not fall below 80°F in several coastal cities. More than 90 local temperature records are expected to be tied or broken through Wednesday, with two-thirds of those likely to be nighttime highs.

"The heat doesn’t necessarily stop when it’s dark out," said Josh Adam, a meteorologist with the National Weather Service in Bismarck, North Dakota, where temperatures are forecast to exceed 100°F (37°C) until Tuesday.

The dome is described as one of the strongest to affect the Dakotas in 25 years, according to senior AccuWeather meteorologist Chad Merrill. Record triple-digit temperatures are anticipated in Nevada, Utah, Colorado, Wyoming, Idaho, Montana, North Dakota and South Dakota. Las Vegas is expected to reach 111°F (48°C) on Saturday.

Officials advise residents to stay hydrated and seek cool environments, noting that prolonged heat can increase fire risk, especially in dry regions such as the Rockies where dry thunderstorms may develop.

Scientists link the intensity and duration of the heat wave to climate change, which is making extreme heat events more frequent and widespread. The current El Niño, still developing, is also expected to amplify temperatures later in the year.