(CNN) -- Few of us look forward to rain on the weekend. But heat-plagued residents from Massachusetts to Minnesota will be jumping for joy as a cold front descends with some soothing showers.
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It will break the grip of the humid heat wave that has smothered the northeast quarter of the nation this week like a musty wool blanket.
The relief will arrive in the upper Midwest late Friday before cooling off the Northeast Saturday night, the National Weather Service said.
People should avoid celebrating outdoors, as thunderstorms are predicted to electrify the ground with lightning in many areas. Michigan could see large hail, the weather service said. High gusts may blow loose objects around.
Tornadoes are also possible.
But the sticky heat will not retreat without a fight. It will steam cook the Midwest during the day Friday and the mid- to north Atlantic until late Saturday.
Temperatures above 90 degrees will combine with roughly 100% humidity to put heat indexes, how hot it feels, near 100.
The index should hit 105 in the heavy populated corridor from Washington to the northern exurbs of New York City and over a broad swath around Detroit, the weather service warns.
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Extreme heat causes more deaths than all other extreme weather conditions, the Centers for Disease Control and Prevention says.
It killed more than 8,000 people between 1979 and 2003, more than "hurricanes, lightning, tornadoes, floods, and earthquakes combined."
From 1999 to 2009, there was an annual average of 658 heat-related deaths in the country, the CDC says.
At least six people have died this summer in the Northeast, health officials in Maryland and New York state reported. A elderly man in Kentucky found dead this week after he wandered away from his home passed away from heat exhaustion, a local coroner said.
The hot weather is of particular concern for children, the elderly and people with heart and lung conditions, as air quality plummets while ozone levels soar. Officials advise everyone to stay cool and drink plenty of water.
As the high pressure area that caused the heat relinquishes in the northeast, a new one will form in the American Southwest.
It will bring "record heat" to western Nevada, the weather service predicts, with temperatures topping 100 degrees in some places every day for nearly a week.
Fire precautions are in place there due to a long-standing drought and dry heat.