The heat wave will be the hottest and longest on record for California for September, he said.
Kay will still be about 220 miles south of San Diego on Friday, according to the National Weather Service in Los Angeles, but the flow around the storm will bring easterly winds to the area, which could bring extreme heat all the way down to the beaches.
The weather service in San Diego extended the excessive heat warning for the region through Friday to account for the possibility of high temperatures well into the 90s to 100 reaching the coast.
Scorching hot temperatures shatter records
Numerous heat records have been set across the West, according to the weather service.
In California, San Francisco airport hit 97 degrees Monday, breaking a daily record. Salinas hit 103 degrees, shattering the previous record of 92 degrees set in 2004. Livermore hit a record high of 116.
Salt Lake City hit 104 Monday, the hottest September day on record and also the 32nd day this year with temperatures reaching at least 100 degrees, beating the previous record by 11 days.
Temperatures in Billings, Montana, reached 100 degrees Monday, which tied a previous record. This was the first time Billings has hit 100 degrees twice in the same September.
Greenhouse gas emissions from human activities have heated the planet by about 1.2 Celsius since pre-industrial times and that warmer baseline means higher temperatures can be reached during extreme heat events, scientists say.
Wildfires ignited throughout the West
The hot and dry conditions also mean that fires will spread more quickly, rage more intensely and burn for longer.
Several destructive wildfires erupted over the past week, with at least four people dying in two California blazes that also burned homes and thousands of acres of land.
The fires, burning simultaneously in parched drought-stricken lands, have choked the hot atmosphere with smoke, bringing unhealthy air quality to parts of the Western states.
The thick smoke, billowing from numerous wildfires, is visible from space, according to images released by the National Oceanic and Atmospheric Administration
The fires have also displaced thousands of residents as the flames advanced on communities, slashing through dry vegetation, and burning homes and cars.
CNN’s Taylor Romine contributed to this report.