SANTA CRUZ, California (AP) — Dozens of wildfires raging throughout Northern California have now claimed at least three lives and threaten tens of thousands of homes, authorities said Thursday.

The death of a resident in Solano County, in the north eastern San Francisco Bay Area, was reported Thursday by Sheriff Thomas A. Ferrara, although he didn’t have any additional details.

A Pacific Gas & Electric utility worker assisting with advance clearing was found dead Wednesday in a vehicle in the Vacaville area between San Francisco and Sacramento. A pilot on a water-dropping mission in central California also died Wednesday when his helicopter crashed.

Governor Gavin Newsom addressed the wildfires, calling them clear evidence of climate change, in a last-minute video recorded for the Democratic National Convention from a forest near Watsonville after he visited an evacuation centre.

“If you are in denial about climate change, come to California,” he said

“I confess this is not where I expected to be speaking here tonight,” he said into what appeared to be a cellphone camera. Newsom had recorded an earlier, more lighthearted video, to be delivered in the convention’s prime-time hours but decided it didn’t bring the right tone amid his state’s disasters, said Dan Newman, one of his political advisers.

More than two dozen major fires were scorching California and taxing the state’s firefighting capacity, sparked by an unprecedented lightning siege that dropped nearly 11,000 strikes over several days.

The fires have destroyed 175 structures, including homes, and are threatening 50,000 more, said Daniel Berlant, an assistant deputy director with the state Department of Forestry and Fire Protection. In all, 33 civilians and firefighters have been injured.

At least two people were missing.

Most of the activity is in Northern California, where fires have chewed through about 500 square miles (1,250 square kilometres) of brushland, rural areas, canyon country and dense forest surrounding San Francisco.

More than 10,000 firefighters are on the front lines, but fire officials in charge of each of the major fire complexes say they are strapped for resources. Some firefighters were working 72-hour shifts instead of the usual 24 hours. The state has requested 375 engines and crew from other states.

“That’s going to allow our firefighters that have been on the front line since this weekend to have an opportunity to take some rest,” Berlant said.