A heat dome can bring dangerously high temperatures. What is it?

PO1 William "Chip" Nagel “If you've made grilled cheese in a pan and you put a lid on there, it melts the cheese faster because the lid helps trap the heat and makes it a little bit warmer,” Lamers says. “It's a similar concept here: You get a big high-pressure system in the upper parts of the atmosphere and it allows that heat to build underneath over multiple days.”