Autumn heat wave to build in California, Arizona, Nevada

Temperatures will soar to record-challenging levels from the southwestern United States deserts to the California coast during much of the week, AccuWeather meteorologists say. Along with surging temperatures will come a renewed wildfire risk.

"A vast zone of high pressure will expand across much of the West this week, allowing for temperatures to climb well above historical average, even along the Pacific coast, where it can be more difficult for temperatures to climb," AccuWeather Meteorologist Haley Taylor said.

When temperatures rise across the interior west, a cool breeze is often pulled in from the Pacific Ocean, helping regulate temperatures along many beaches and the Interstate 5 corridor. In this case, however, the flow will turn offshore, and the ocean's cooling effect will be minimal or not occur at all.

The San Francisco Bay Area will be one coastal hot spot in the pattern this week. Following highs in the 60s Fahrenheit this weekend, which is several degrees below average, high temperatures will trend upward into the 80s on Monday and then well into the 90s on Tuesday. Under the right conditions, the record of 97 set in 1980 could be challenged. The heat wave will bring the highest temperatures of the year for San Francisco. Thus far, the highest it has been at the airport was 88 on July 2.

Los Angeles will feel the heat in the pattern as well, although temperatures are likely to stop well short of high marks well above 100 degrees earlier this month. On Sept. 6, the temperature reached 112 in downtown Los Angeles, which was just 1 degree shy of tying the all-time record of 113 set in on Sept. 27, 2010. Highs will generally be in the 80s in downtown Los Angeles this week, but may reach the low 90s on Wednesday. As such, temperatures will be 5-10 degrees above the historical average.

The desert cities of Las Vegas and Phoenix will be plenty hot in the pattern this week. In both cities, record-tying or record-breaking temperatures are forecast each day from Monday through Saturday of this week and will be at or above 100 through Friday in Las Vegas and through Saturday in Phoenix. In Phoenix, temperatures may get to within a few degrees of the all-time September high of 116 set on the 1st of the month in 1950 and again this year on the 5th.

Experts urge that as temperatures climb, people should ncrease their intake of non-alcoholic, non-caffeinated fluids, especially when working or exercising outdoors.

Surging heat, low humidity levels and dry vegetation are prime ingredients for wildfire ignition, and people should avoid the use of open flames and be cautious when using any equipment outdoors that can produce sparks.

"Along with stiff offshore breezes, there will be an increased risk of wildfires across Southern California, mainly in the mountains and foothills, through Wednesday," Taylor said.

Breezes could drive any fires that develop toward coastal locations.

The ongoing Line, Bridge, and Airport fires have burned over 100,000 acres, but all are almost fully contained. The Line Fire had the lowest containment, at 83%, as of Saturday afternoon.