Some parts of the U.S., such as Phoenix, Arizona, are famously hot without the mugginess. Phoenix and nearby desert regions experience this so-called “dry heat” due to being located far away from large water bodies, mountains that block moist air masses and weather patterns that bring scarce precipitation.

Major cities across the United States are preparing for extreme temperatures caused by a heat dome that hit the U.S. Plains on Friday and is expected to expand to much of the rest of the country over the coming days.