Power has been shut off in wind-prone parts of Northern California to prevent sparking wires from igniting new wildfires during a new round of gusty, dry weather.

Pacific Gas & Electric’s online map of public safety power shutoffs shows large clusters of outages in the northern Sacramento Valley and the northern Sierra Nevada foothills and a few elsewhere early Thursday. About 32,500 customers are affected in nine counties.

The utility says up to 37,000 customers could be affected in 15 counties.

In Southern California, investigations have found that damaged electrical equipment ignited two wildfires a year ago, including the Easy Fire that threatened the Ronald Reagan Presidential Library and Museum.

The Ventura County Fire Department says the fire that threatened the library started when an insulator attached to a high-voltage power line swung into a steel power pole during winds.

The department also says the larger Maria Fire, which consumed just shy of 10,000 acres after sparking the next day, was caused when a conductor on an electrical line separated and touched a metal pipe.