By Alex Dobuzinskis
LOS ANGELES, Oct 4 (Reuters) - The fall season has brought a wave of hot, dry weather to California, with parts of the state baking this weekend in triple-digit temperatures and officials expressing concern the summer-like heat could spark a massive wildfire.
The scorching temperatures came from a high pressure system in the U.S. West and the arrival in Southern California of autumn's first Santa Ana winds, which carry hot air through mountain passes toward the coast, meteorologists said.
In Los Angeles, thermometers in parts of the city's sprawling San Fernando Valley could read 100 to 105 degrees Fahrenheit (38 to 41 degrees Celsius) on Saturday, said National Weather Service meteorologist Scott Sukup.
Elsewhere in Southern California, officials expected high temperatures for Ventura, Orange and San Diego counties. Sukup said high temperature records for this calendar day could fall in certain parts of the region.
Even the more temperate San Francisco is expected to sizzle on Saturday, with the Weather Service in a public advisory forecasting temperatures of 78 to 85 degrees Fahrenheit (26 to 29 degrees Celsius) in the city and as high as near 100 degrees (38 Celsius) in valley areas to the south.
The heat wave has put California firefighters on high alert. State officials have placed a full force of 8,000 firefighters at the ready, as crews near full containment of two massive blazes burning in Northern California.
"Conditions remain ripe for a new fire," said Daniel Berlant, spokesman for the California Department of Forestry and Fire Protection.
Historically, California has experienced some of its largest, most devastating wildfires in the fall, he said.
Winds are not as high as they were earlier in the week, when officials issued a red flag warning for Los Angeles and Ventura counties because of the threat of those winds turning a small fire into a massive conflagration.
The warning expired on Friday but meteorologists said high temperatures are expected to continue through the weekend before cooler air blows in from the Pacific Ocean on Monday.
Before then, the heat will likely pose a challenge to thousands of bicyclists who will pedal through downtown Los Angeles and the city's eastern sections in an event called CicLAvia planned for Sunday.
Weather Service officials have called on people in California to limit outdoor activities. (Reporting by Alex Dobuzinskis; Editing by Frank McGurty and James Dalgleish)