Communities in wildfire-prone Northern California have an array of emergency systems designed to alert residents of danger: text messages, phone calls, emails and tweets.
But after days of raging blazes left at least 23 dead, authorities said those methods will be assessed after some residents complained those warnings never got through.
The fast-moving fires, strengthened by fierce winds and nearly absent humidity, began to burn through the state's fabled wine country Sunday (Monday NZT) night.
Counties used a variety of ways to send out warnings, but the alert systems rely on mobile phones, landlines or the internet to rouse residents.
"People were in bed, asleep at midnight, and these fires came down on these communities with no warning within minutes," said state fire agency Chief Ken Pimlott.
"There was little time to notify anybody by any means," he added.
Sonoma County used various systems in an attempt to alert residents of the approaching flames but also decided against using what's known as a Wireless Emergency Alert, a widespread message sent to cell phones in the region, sometimes compared to an Amber Alert issued for missing children.
Because of its broad reach, officials concluded the message could panic people not in danger, triggering unnecessary evacuations that would snarl traffic and delay emergency vehicles, said county spokeswoman Jennifer Larocque.
"They would have reached many people not affected by the fire," she said. "It would have delayed our response."
In emergencies where a few minutes or even seconds can save lives, the notification systems have inherent blind spots. Not everyone will get the message.
Sonoma County uses a service that sends out text messages or emails when an evacuation is ordered, but residents have to sign up to receive them.
The county also uses a mobile phone app that can receive messages, but again it requires a resident to opt-in to participate.
The county can also trigger automated emergency calls to landlines in an area threatened by fire, but that would only reach homes with those phones.
The Sonoma County Sheriff's Department said the county's emergency alert service texted thousands of warnings to residents to flee Sunday night (Monday NZT).
However, nearly 80 cellphone towers were knocked out or badly damaged, officials said.
Some evacuees escaped only when they realized the fire was nearly at their doors.