Pacific Gas & Electric Company (PG&E), the bankrupt SF-based utility that provides power to some 16 million Californians, is warning customers that it could shut off electricity in entire cities—including San Francisco—for up to a week as part of its new fire-prevention safety measures.

In a message sent via email to many PG&E customers in recent months, the utility warns that it may suspend electrical service “for a minimum of 24 hours and up to a week” if there’s reason to suspect that live power lines may pose a particular danger of starting fires.

PG&E’s “public safety power shutoff” site explains:

Given the continued and growing threat of extreme weather and wildfires, and as an additional precautionary measure following the 2017 and 2018 wildfires, we are expanding and enhancing our Community Wildfire Safety Program to further reduce wildfire risks and help keep our customers and the communities we serve safe. This includes expanding our Public Safety Power Shutoff program beginning with the 2019 wildfire season to include all electric lines that pass through high fire-threat areas – both distribution and transmission.

San Francisco is not one of the regions PG&E considers particularly at risk for a shutoff. However, the company cautions “power may also be shut off if [a] community relies upon a line that passes through an area experiencing extreme fire danger conditions.”

Therefore “any customer who receives electric service from PG&E should be prepared for a possible public safety power outage” which could theoretically last up to seven days.

Financial liability for wildfires started by PG&E equipment—including the Camp Fire, the worst fire ever recorded in California, which killed 85 people—directly led to the company’s declaration of bankruptcy earlier this year, and criminal charges for the company or its executives are still possible.

“No single factor will drive a public safety power shutoff,” the company warns, but variables like red flag warnings, low humidity, winds over 25 miles per hour, and dry ground conditions could all contribute to a decision to pull the plug.

PG&E customers—virtually all of Northern California—should pay attention to fire warnings and prepare for a potential long-term blackout.

The company staged a shutoff drill in Orinda last week in preparation, and future drills may be pending.