If you're reading this in the large swath of the United States where temperatures are in the triple digits, you don't need us to tell you it's hot outside. But maybe you'd like us to tell you why -- there is a "heat dome" out there.
According to the Associated Press, Eli Jacks, a meteorologist with the National Weather Service explains that the dome is formed when a huge area of high pressure compresses hot, moist air beneath it. When that happens, the air below it sinks and compresses because there's more weight on top, causing temperatures in the lower atmosphere to heat up.
The dome of high pressure also pushes the jet stream and its drier, cooler air, farther north, while hot, humid air from the Gulf of Mexico circulates clockwise around the dome, traveling farther inland than normal.
The dome started in the plain states, and is now spreading all the way to the Eastern seaboard.
Temperatures in parts of North and South Dakota, as well as Nebraska, have soared above 100 -- a rarity there. 25 local records were set on Monday. Temperatures of between 90 and 100 are hitting such cities as Chicago, Boston, New York, Philadelphia and Washington, D.C. and are expected to last through the weekend.
(By the way, here in sunny Los Angeles it is a very comfortable 80 degrees or so -- not to brag or anything).
All of those people using their air conditioners to combat the heat is stressing the nation's power grid.
"These are the days everyone wants to have their ACs on, their computers going while they watch TV," said Jon Jipping, COO of ITC Holdings Corp., a grid operator in several Midwest states. "These are the days we get ready for."
Utility companies said they are ready, that their lines have not yet reached capacity. They predicted that widespread electrical outages are unlikely.