Today's temperature in Las Vegas could equal the city's all-time high of 117.
Yesterday, it was 115 in Las Vegas, tying the city's record for the date.
The heat wave has sent more than 40 people to hospitals. Most of them were attending an outdoor concert yesterday.
Organizers also cited the heat for their decision to cancel today's Running with the Devil marathon in Boulder City, 20 miles south of Las Vegas.
In the Reno area, federal land managers installed sprinklers in effort to reduce the heat in outside pens of the largest wild-horse adoption facility in the country.
Friday's high of 103 in Reno broke its record of 100 for the date set in 2010.
Much of the West is baking in one of the worst heat waves in years.