(Adds company expectation to restore power, two other utilities announce cuts)
By Peter Szekely
Oct 15 (Reuters) - California's largest public utility cut off electric power to about 60,000 customers to prevent wildfires such as those that erupted in the state's wine country last fall, as high winds threatened to topple trees and power lines this week.
With gusty winds and low humidity in the forecast this week, Pacific Gas & Electric warned customers on Sunday that their power would be cut. The company initially said the blackout would last until at least Monday evening, and some schools canceled classes in the six affected northern California counties.
But by Monday afternoon, the company said it expected to restore power to 70 percent of affected customers by midnight.
"This is the first time that we have proactively turned off the power due to fire threat conditions," said Melissa Subbotin, spokeswoman for the utility, which is owned by PG&E Corp .
The power outage, which started on Sunday, came just days after California's Department of Forestry and Fire Protection found that last year's Cascade Fire in Yuba County, which burned nearly 10,000 acres and killed four people, was started by "sagging power lines coming into contact during heavy winds." One of the lines was owned by PG&E.
With PG&E facing billion of dollars in potential payouts from lawsuits, California lawmakers in September passed a bill that could help the utility avoid potentially crippling liabilities.
Two smaller California utilities, San Diego Gas & Electric and Southern California Edison also announced power cuts to some communities because the seasonal Santa Ana winds blowing off the deserts of southeastern California presented an extreme danger.
PG&E's move prompted many customers to complain on Twitter that the outage was spoiling food, disabling traffic lights and keeping them from doing their jobs.
Due to the disruption to customers, the power cutoff was a "last resort" measure as part of a program that includes a team monitoring weather and other conditions in several high-risk counties, especially during wildfire season, typically late summer and fall, Subbotin said.
"We take into consideration climate change here as the new normal," she added. "That has unfortunately increased the risk of wildfires."
Customers were warned of the cutoff by telephone, text message and email, Subbotin said.
The Konocti Unified School District in Lower Lake, California, which includes 3,500 students, was one of four Lake County districts that closed, Superintendent Donna Becnel said.
"I always hate to cancel school," Becnel said by telephone. "But with the number of power outages and not knowing how long it was going to last, there was no way to have classes without heat, lights and the ability to provide food for students."
Reporting by Peter Szekely in New York; Additional reporting by Suzannah Gonzales in Chicago; Editing by Lisa Shumaker, Richard Chang and Diane Craft