Large swaths of the Golden State this week are almost completely dark, but the nation’s top network operators claim cellular service has been largely resilient. California’s utility companies preemptively shut off power on Wednesday, beginning in the northern reaches of the state and heading down almost 800 miles to the south, in a bid to prevent antiquated infrastructure from causing wildfires.

Up to 800,000 Northern and Central California business and residential customers woke up without power this morning. High-wind advisories are rolling southbound, and more than 173,000 customers in Southern California are still expected to lose power amid strong Santa Ana winds and low humidity.

The state hasn’t faced widespread electrical outages like this since energy traders, most famously Enron, caused the California electricity crisis of 2000 and 2001 by creating artificial shortages to increase prices. Devastating and increasingly deadly wildfires, which were caused by power lines, have led the state’s utility companies to initiate more preemptive measures to reduce the risk.

While some customers are complaining about cellular service disruptions on social media, networks are still active across most of the state.

Verizon says it has a comprehensive backup power strategy in case commercial power is lost during an emergency or extreme weather event. “We have generators and backup batteries at the majority of our cell sites, and all of our switch locations to keep our network up and running if commercial power is lost,” a company spokesperson said. The company adds that it is prepared to refuel generators as needed to ensure service remains active.

AT&T, which describes this as an “unprecedented event,” says it has open lines of communication with PG&E and SoCal Edison, the state’s largest power providers, to make sure it prioritizes its resources accordingly. “Like all PG&E customers, we are also affected by this power shutdown. Overall our network continues to perform well. We are aware that service for some customers may be affected by this event and are working as quickly as possible to deploy additional generators and recovery equipment,” an AT&T spokesperson said.

PG&E, the company that serves 16 million customers in the northern and central parts of California, filed for bankruptcy earlier this year and faces an estimated $30 billion in legal liabilities for multiple deadly fires caused by its grid.

T-Mobile US also pointed to permanent generators that are housed in key cell sites as a primary means of avoiding service disruptions. “In addition to backup power, we have a fleet of temporary generators that our emergency response teams can deploy if needed to get sites back up and running,” a T-Mobile spokesperson said. “Our network is holding up well with only a small number of sites down in some of the areas affected by the power shut off.”

Sprint, like its competitors, encouraged impacted customers to prepare for potential outages by stocking up on supplies and subscribing to alerts from local and state agencies. “The power shut offs may impact cell sites in the area,” the company wrote in a blog post. “Some of Sprint’s cell sites may have permanent generator power available. For others, the company is actively deploying portable generators as much and as quickly as possible.”

Residents in 38 of California’s 58 counties are expected to be impacted by the ongoing shut downs. While earlier reports indicated power might remain off for up to seven days in some areas, most of the state’s electrical grid is expected to be fully operational in the next couple days.