In several states, such as California, Oregon and Idaho, it is expected to be over 40 degrees hot and the NWS warns of heat-related deaths.
The heat, which coincides with severe drought, has already claimed the lives of at least 116 people in Oregon alone.
The heat wave that is now sweeping across the country comes after a June month that broke a record as the warmest since the measurements started 127 years ago, according to the weather authority NOAA.
The heat and drought have led to a large number of forest fires in western North America. In the Canadian community of Lytton, where the record temperature was recently measured at 49.6 degrees, residents were able to return for the first time on Friday to what remains of their homes. On June 30, they were forced to flee headlong from a forest fire that destroyed nearly 90 percent of the city.