A large high-pressure system creating record-breaking heat across the southwestern United States is expanding eastward and may become one of the most geographically extensive heat waves in American history, according to meteorologists.

The heat dome has already broken March temperature records in 14 states: California, Arizona, Nevada, Kansas, New Mexico, Nebraska, Utah, South Dakota, Missouri, Iowa, Colorado, Wyoming, Minnesota and Idaho. On Friday, four locations in Arizona and California reached 112 degrees Fahrenheit, setting a new record for the hottest March day in the continental United States and exceeding the previous record by 4 degrees.

The National Weather Service's Weather Prediction Center reports that temperatures in the 90s are expected across the southern and central Plains by Wednesday, with one-quarter to one-third of the continental United States potentially approaching March records. The heat dome is forecast to persist through the middle of next week as April begins.

The National Center for Environmental Information recorded at least 479 weather stations breaking March records from Wednesday through Saturday, along with 1,472 daily temperature records during the same period. The system is being sustained by a jet stream that has become stationary, extending as far west as Hawaii, where storms are bringing heavy rain and flooding.

Climate scientists from the World Weather Attribution group determined Friday that the record heat was made 800 times more likely due to climate change from burning fossil fuels. The group calculated that human activities added at least 4.7 degrees to the temperatures being recorded.

Weather historian Chris Burt noted that while the physical area of this heat wave likely exceeds historic events from 2012 and 2021, it may not match the Dust Bowl heat waves of 1936, which occurred as a series over two summer months rather than a single event. Meteorologists expect the heat dome to move eastward and dissipate by late next week.