SAN FRANCISCO (AP) — California’s biggest utility shut off electricity to more than a million people Wednesday for what could be days on end, in the most sweeping effort in state history to prevent wildfires caused by windblown power lines.

The move came after two years of catastrophic fires sent Pacific Gas & Electric into bankruptcy and forced it to take more aggressive steps to prevent blazes.

The utility said it cut power to more than 500,000 customers in Northern California and that it plans to gradually turn off electricity to nearly 800,000 customers to prevent its equipment from starting wildfires during hot, windy weather. A second group of about 234,000 customers will lose power starting at noon, the utility said. The power outages are expected to affect about 2.5 million people.

Deliberate outages like these could become the new normal in an era in which scientists say climate change is leading to fiercer blazes and longer fire seasons.

The utility plans to shut off power in parts of 34 northern, central and coastal California counties to reduce the chance of fierce winds knocking down or toppling trees into power lines during a siege of hot, dry, gusty weather.

Gusts of 35 mph to 45 mph (56-72 kph) were forecast to sweep a vast swath of the state, from the San Francisco Bay area to the agricultural Central Valley and especially in the Sierra Nevada foothills, where a November wildfire blamed on PG&E transmission lines killed 85 people and virtually incinerated the town of Paradise.

The California Department of Forestry and Fire Prevention said it increased staffing in preparation for extreme fire weather.

The winds will be the strongest and most widespread the region has seen in two years, and given the scope of the danger, there was no other choice but to stage the largest preventive blackout in state history, PG&E said.

“This is a last resort,” said Sumeet Singh, head of the utility’s Community Wildfire Safety Program.

However, people should be outraged by the move, Gov. Gavin Newsom said. “No one is satisfied with this, no one is happy with this,” he said.

The utility needs to upgrade and fix its equipment so massive outages are not the norm going forward, he said.

It could take as many as five days to restore power after the danger has passed because every inch of power line must be checked to make sure it isn’t damaged or in danger of sparking a blaze, PG&E said.