By Jeanine Santucci USA TODAY
Most of the nation can expect above-average temperatures in coming days as a giant heatwave is expected to spread across much of the continental U.S. beginning this week.
The heatwave will bring temperatures at least 5 to 10 degrees higher than average to much of the country, according to estimates by the National Oceanic and Atmospheric Administration, which predicts a high probability of above-average temperatures for most of the U.S. over the next several days.
Add in climbing humidity, and many people will experience temperatures that will feel well over 100, according to Capitol Weather Gang meteorologist Mike Cappucci. The heat is a sign of a coming “heat dome,” he said.
Temperatures in the mid-100s are forecast for eastern Montana, the Upper Missouri Valley, and South Dakota in the first half of the week. Heat indexes could be over 110 in urban areas such as St. Louis, with a slight cool-down possible by the end of the week in some areas.
Later in the week, areas of Oregon, Idaho, and Washington probably will see temperatures into the 100s
A heat dome is the result of a strong change in ocean temperatures from west to east in the tropical Pacific Ocean during the preceding winter, according to the National Ocean Service. The warm air coming from the west part of the Pacific Ocean gets trapped in the jet stream as it approaches land. When that hot air arrives over land, the atmosphere traps it. Winds can move the heat dome around.
