Cristy Thomas began to panic as she called 911 for the second time on a warm October day but couldn’t get through. She anxiously watched the plume of black smoke pouring over her rural community in central California get larger.

Then she heard a familiar ping.

Watch Duty, an app that alerts users of wildfire risk and provides critical information about blazes as they unfold, had already registered the fire. She relaxed. The cavalry was coming.

“I can’t tell you the sigh of relief,” she said, recalling how soon after sirens blared through the neighborhood and helicopters thundered overhead. “We were seeing it happen and we had questions – but Watch Duty answered all of them.”

Thomas is one of millions of Watch Duty evangelists who helped fuel the meteoric rise in the app. In just three years since it launched, the organization now boasts up to 7.2 million active users and up to 512m pageviews at peak moments. For a mostly volunteer-run non-profit, the numbers are impressive, even by startup standards. But they are not surprising.

Watch Duty has changed the lives of people in fire-prone areas. No longer left to scramble for information when skies darken and ash fills the air, users can now rely on an app for fast and accurate intel – and it’s free.

It offers access to essential intel on where dangers are, with maps of fire perimeters, evacuation areas and where to go for shelter. Users can find feeds of wildfire cameras, track aircraft positions and see wind data all in one place. The app also helps identify when there’s little cause for alarm, when risks have subsided, and what agencies are working in the trenches.

“The app is not just about alerts, it is about a state of mind,” Watch Duty’s CEO, John Mills, said. The Silicon Valley alum founded the organization after moving from San Francisco to a sprawling ranch in Sonoma county where fire dangers are high. After starting in just four California counties, Watch Duty covered the entire state in its first year before rapidly expanding across the American west and into Hawaii.

As the community has grown – reaching people across 14 states in 2024 – new features and enhanced precision have accented its popularity, and according to Mills, filled unmet needs.

In the past years, it’s not just residents who have come to rely on the app. An array of responders, from firefighters to city officials to journalists are also logging on, ensuring key actors are on the same page.

“People always thank me for Watch Duty, and I am like, ‘you’re welcome – and I am sorry that you need it,’” Mills said. But it’s clear that the need is real. In each new area where they have offered the service, word of mouth has driven usage.

“We spent no money on marketing at all,” Mills said. “We just let the genie out of the bottle so the world would know things could never go back to the way things were.”

The app sprouted out of an emergency information ecosystem on social media that has for years communicated unofficial information. But unlike other platforms that seek to capture user attention and keep it there, Watch Duty has no algorithms that filter or muddy important information.

It relies on volunteers dubbed “reporters” who listen for emergency updates in the low hum of radio static, analyze data from the National Weather Service and other sources, and discuss findings with one another before sending push notifications to their active user base.

Run by real people, including active and retired wildland firefighters, dispatchers and veteran storm watchers, the team collaborates to quickly gather and vet information when a fire ignites.

An automated dispatch relays 911 alerts via Slack, kicking Watch Duty reporters in the particular region into action. Radio scanners, wildfire cameras, satellites and announcements from officials are scoured for intel. When conditions are confirmed they post the information, adding a push notification to users in the area if there’s a threat to life or property.

The network is fueled by hundreds of people who donate their time and a small staff of just 15 reporters and engineers. Together, they have alerted the public to more than 9,000 wildfires this year.

Meanwhile, support has been pouring in. This year Watch Duty received $5.6m in funding from grants, individual donors and a new professional subscription model that offers paying users insights into things like where electric and gas transmission lines intersect the fire footprint, lands managed by utilities, private owners, and agency responsibility areas – plus a search function for historical and inactive fires.

But this is just the beginning, according to Mills.

“I didn’t call this ‘Fire Duty’ on purpose,” he said, a nod toward the plan to begin reporting on other risks in the near future, including flooding and extreme weather events.

As the climate crisis turns the dial up on severe storms, the model has also showcased the important role critical information can play in helping at-risk communities adapt. Along with empowering residents in moments of chaos, the app has started conversations at the highest levels of government about communication gaps and challenges during disasters.

Watch Duty was one of a few select companies invited to weigh in during a White House roundtable on fire this year, an enormous step from the initial pushback they received from local officials after launch who were worried information on the platform would incite panic or spread misinformation.

“No one gave us approval to do this,” Mills said. “It was [built] from the bottom up – from the back of the woods to the White House.” Other agencies have also been utilizing their services, enticed by the one stop shop of easy-to-use intel.

The Idaho department of lands uses a direct feed from Watch Duty on their own site. Back when he first launched the app, Mills told the Guardian he hoped the then tiny team would become “so important, so loud, and so obnoxious that we can’t be ignored”. Now, he’s working directly with burn bosses, incident management teams and agencies like California state parks.

But the most important stakeholders driving Watch Duty’s momentum are people like Cristy Thomson who look to the app to navigate the chaos caused by catastrophic fire. The blaze that erupted near her home last October was far from the first.

Thompson was one of thousands affected by the CZU Lightning Complex fire, which consumed more than 80,000 acres across the Santa Cruz mountains, destroying 1,490 homes and other structures and claiming a life.

Her home was spared. But during disasters she helps evacuate horses and other animals, an undertaking that adds extra layers of chaos and the need for coordination. Before Watch Duty, she said there were many more challenges.

Uncertainty and confusion among residents has often ended in heartbreak for the horse community that rushes in when catastrophes strike, she said. Frenzied evacuations can mean more animals are left behind.

“It was such a comfort knowing we weren’t the only ones on the face of this earth who knew there was a fire up there,” she said. “We knew they were throwing everything they had at it.”

It’s why she welcomes the admittedly “obnoxious” ping when it sounds on her phone. She’s grateful to the volunteers who watch and the reliable information they provide and hopes even more people will have Watch Duty buzzing in their pockets in the years to come. The app has been “heart-savingly useful twice”, she said.

“The biggest thing is you know you can trust it,” she added. “That’s the value.”