Forecasting from the National Weather Service predicts a high of 126 in Death Valley, California. Phoenix, Arizona, expects a high of 117 on Sunday, and Las Vegas, Nevada, is preparing for weekend highs of 113.
The National Weather Service uses different criteria for heat advisories in different parts of the country. An excessive heat warning indicates unusually high temperatures that could pose considerable health risks.
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In the southwest, "we use what we call a heat risk," said Marvin Percha, National Weather Service meteorologist. This is different from other areas of the country where heat indexes take a bigger importance in heat warnings.
"We look at how rare the event is and compare what's normal," Percha said. "Considering the temperatures we have forecast now, we're looking at a pretty rare event."
Heat in Phoenix this weekend could break daily records. Phoenix's expected high of 117 on Sunday would beat the daily record for July 12 of 115, set in 2009. Heat in California and Nevada will come close to records, but not quite meet them.
High heat is seasonally appropriate for the region, just usually not so high for so long.
Friday marks the 107-year anniversary of the hottest day ever recorded on earth, when Death Valley hit 134 degrees Fahrenheit, said CNN meteorologist Pedram Javaheri.
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Temperatures this high can be amplified in valleys and on the ground, where materials can begin to melt.
While monthly records might not be broken this weekend, excessive heat is part of an overall trend of rising temperatures. High heat patterns are just one of many extreme weather events exacerbated by climate change.
High temperatures can be dangerous, and people in affected areas are urged to take safety precautions. "Anyone with heart or diabetic issues should be particularly careful about this and really do their best to really stay out of it," Percha said.
According to the Centers for Disease Control, heat-related sickness kills over 600 people per year. Stay safe by remaining indoors, keeping hydrated, wearing lightweight clothing, and knowing the symptoms of heat sickness.
"If you have to be outside, try to limit your exposure and keep yourself well hydrated," Percha said. "Seek air conditioned cooling centers if you have to."
Phoenix has a map of public cooling centers. Check with local officials to find your nearest cooling center or water donation spot.
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