Heat dome to bake much of US with dangerous record temperatures

Forecasters in Bismarck issued an Extreme Heat Warning for all of western and central North Dakota from Saturday afternoon through Monday evening as a broad heat dome spread across the Lower 48 and threatened to push temperatures far above normal. More than 90 local temperature records could be tied or broken through Wednesday, and about two-thirds of those records would be overnight lows, a sign that the danger would not end when the sun went down.

The hottest readings were expected to hit parts of Nevada, Utah, Colorado, Wyoming, Idaho, Montana, North Dakota and South Dakota, where triple-digit highs were likely. In North Dakota, temperatures were forecast to climb above 100 degrees Fahrenheit through Tuesday, well beyond the state’s usual summer highs in the 80s. The heat could run 15 to 25 degrees above normal in many places, with some areas feeling the effects into the end of the month.

The dome broadens across as much as two-thirds of the continental United States. When overnight temperatures stay high, the body gets less relief after a hot day, making recovery harder and raising the chances of heat illness.

The people most at risk are older adults, especially those with pre-existing diseases, limited mobility or no one checking on them at home. People who live alone are more vulnerable during extreme heat. Outdoor workers face a separate threat, and co-workers should take breaks to cool off, drink water and seek medical care immediately if heat illness symptoms appear. People without reliable air conditioning are left with the least protection when hot nights linger.

A heat dome forms when persistent high pressure traps heat over an area and blocks the cooling winds and cloud formation that would normally bring relief. The jet stream’s meanders are one reason these systems can linger for days to weeks.