Various heat alert in effect Wednesday and Thursday over large parts of the United States (National Weather Service)

Today alone, 141 million Americans are under heat advisories or heat warnings from the Midwest to the Ohio Valley. That’s after 78 million were afflicted by extreme heat Tuesday over an area the size of Mexico. By far, the most impressive heat and humidity records yesterday occurred in Minnesota, where Minneapolis had its most humid day on record.

Minneapolis Star Tribune meteorologist Paul Douglas reports the Twin Cities recorded a maximum heat index of 119 Tuesday, tying its all-time record. Minneapolis also set a new (unofficial) record for dew point temperature (a measure of humidity), which reached at least 82 degrees.

Amazingly, Douglas found Moorhead, Minnesota - located just over the border from Fargo (North Dakota) - had its heat index soar to a sweltering 134 degrees, the hottest on record for the state. It’s dew point climbed to 88, also a state record. Moorhead’s heat index was the highest anywhere in the entire world Tuesday!

NOAA’s Hydrometeorological Center lists some of the other stifling heat index values that swelled from Texas into Canada (the dew point in Hallock, Mn. - at the U.S./Canadian border reached 86, “higher than Dubai or any reporting station in the Middle East” Douglas said). Here’s a small sample:

Prairie Du Chien, Wisconsin: 116
For Hood, Texas: 111
Memphis, Tennessee: 112
Aberdeen, South Dakota: 119
Offut Air Force Base, Nebraska: 112
St. Louis, Missouri: 110
Newton, Iowa: 129
Indianoplis, Indiana: 110
Champaign/Urbana, Illinois: 117

Fortunately, after one more day of oppressive heat, a reprieve is on the way for Minnesota and other portions of the north Central U.S. later today and Thursday. As the National Weather Service writes today on its Facebook page:

After several days of deadly heat and humidity — with as many as 13 fatalities potentially related to the heat wave in the Midwest — relief will finally come later today and tomorrow in the form of a cold front currently moving across Montana, which will significantly drop temperatures across the north central U.S. for the rest of the... week, though locations across the central and southern Plains and parts of the Midwest will not see much change from the extended period of heat.

Chicago WGN meteorologist Tom Skilling blogged that Chicago may reach 100 today for the first time six years. Chicago has seen its hottest temperatures in 34 years so far in July Skilling said.

While the heat is gradually smushed south in the central U.S., it will rebound up the East Coast. Triple digit readings will extend to Philadelphia on Thursday. And as I showed in my post yesterday, by Friday, heat indices of at least 105 are forecast to extend from southeast Georgia to New York City with a large pocket of 110-115+ values in the mid-Atlantic.

Want to find a cool place? Check out Seattle - where highs are forecast in the 60s for the next several days. Local meteorologist and blogger Cliff Mass has been lamenting the unseasonably cold weather there. In his latest blog he writes: “We look to the heavens and ask: Why do we suffer? Why is the warmth of summer denied us?” He then provides an excellent explanation of how the hot weather locked in the central and eastern U.S. is interconnected with the cold weather in the Pacific Northwest.

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Thursday at 1 p.m.: Live video discussion about heat wave (send your questions now)