The National Weather Service (NWS) warned on Monday that “summer has arrived out West with the first significant heat wave of the year.”
Excessive heat warnings and heat advisories have been issued by the service across the areas, who warned that isolated areas could see up to 110 degrees.
According to ABC News cities in Northern California smashed records on Monday with Sacramento reaching 104 degrees while Redding reached 109.
The broadcaster said that on Tuesday Bakersfield, California could see 107 degrees with Las Vegas seeing 105. Residents in Medford, Oregon, and Phoenix could see 104 degrees.
CNN reported that more than 130 heat records could be broken this week in the West as the heatwave sweeps through the areas.
In Las Vegas, the NWS warned that “temperatures will be well-above average this week” with Wednesday to Friday being the hottest days.
In regional areas of California, the service warned of “dangerously hot conditions with high temperatures of 101 to 107 degrees”.
The state, along with southern Oregon, is under heightened risk of fires in the heatwave, with authorities warning residents to be extra cautious with burning outdoors, reports said.
The NWS in Medford, a city in southern Oregon, has issued a fire weather watch, warning of possible lightning and saying that high fire danger could result in new fire starts.
"Please be extra cautious with anything that could start a fire in the coming days by being sure it is no longer burning when you discard it,” the weather service warned.
They added: “Be sure to extinguish all campfires in areas where they are permitted before leaving the area.”
During such high temperatures, the agency says residents should drink plenty of fluids, stay in air-conditioned rooms and away from the sun.