Heat records are falling amidst a historic and brutal heatwave across California.

The heatwave baking parts of the western US has led to excessive heat warnings and advisories for more than 45 million people.

Temperatures are currently 10 to 15 degrees above normal for the time of year, with 47.2C recorded in Fairfield, North Bay of the San Francisco Bay Area on Tuesday August 6th.

Sacramento also hit 46.7C, breaking it's all-time record; over 150 temperature records could be set or tied by the end of the week.

The oppressive heat has fuelled wildfires and caused power outages with California residents urged to reduce electrical consumption in the evening hours.

The Mill Fire in Siskiyou County burned an estimated 4,254 acres as of Saturday evening, with another fire in Los Angeles county burning through over 5,000 acres.

The heat dome producing this heatwave looks to slowly spread eastward into the central and northern plains by mid-week.

However relief isn’t necessarily guaranteed just yet, with Hurricane Kay expected to dictate the weather patterns in the coming days.

Kay is due to bring strong winds and heavy rain to the Mexican coast, still over 200 miles from San Diego on Friday, but it’s flow could bring easterly winds to the area, which could prolong the heat.