Southern California, Nevada and Arizona have seen record-breaking temperatures and hospitalizations due to the intense heat.
At a concert in Las Vegas on Friday, 200 people were treated for heat exposure. The National Weather Service warned of a "life-threatening heat event" to hit the state this weekend.
Temperatures in Nevada were expected to reach 2005 levels, a heat wave during which 17 people died.
In Phoenix, temperatures reached 116 on Friday - just short of the expected high. The Associated Press reported that the likely reason for the lower temperature was that fumes from wildfires had shielded the sun's rays over the city.
Temperatures in the city are expected to reach 120 over the weekend.
California has also seen high temperatures. Death Valley, which recorded the highest ever temperature in the world - 134 degrees - may reach 130 degrees this weekend.
The extreme heat will also touch parts of Idaho and Wyoming.
The Associated Press reported that the high temperatures could affect flights and zoo animals were being put on watch.