A series of fire tornadoes — genuine twisters made of smoke and flame — struck Lassen County, Calif., on Saturday, churning around as the Loyalton Fire rapidly expanded to more than 20,000 acres. Extreme fire behavior and pinpoint lightning strikes accompanied the massive blaze, which was 5 percent contained Sunday morning after burning for two days.

The powerful fire and potent rotation inside the wildfire even prompted the National Weather Service in Reno, Nev., to issue what is believed to be the first weather alert of its kind: a “fire tornado warning.”

“Amazing event. Not aware of this ever before,” wrote Neil Lareau, who studies extreme fire behavior at the University of Nevada at Reno. Lareau’s research helped confirm the existence and intensity of the deadly fire tornado associated with the 2018 Carr Fire in Redding, Calif.

Fire tornadoes contain tornadic wind speeds that form when a smoke plume behaves like a thunderstorm. Saturday’s quickly-swelling wildfire produced a smoke plume that towered 30,000 feet high and began spitting out lightning strikes. It also tapped into a change of wind speed and direction with altitude, and began to rotate.

Doppler radar data indicates five or more tornado-strength vortices may have occurred between 1 p.m. and 3 p.m. Pacific time.

Social media videos captured several of the incredible tornadoes, shrouded in amber haze and smoke, and reminiscent of scenes from a horror movie.

At 2:35 p.m., the National Weather Service in Reno issued a tornado warning for parts of Lassen County in northern California, warning that “a pyrocumulonimbus from the Loyalton Wildfire is capable of producing a fire induced tornado and outflow winds in excess of 60 mph."

“This is an extremely dangerous situation for fire fighters,” read the warning.

Pyrocumulonimbus is the name assigned to a smoke cloud that begins rising and behaving like a typical thundercloud.

Ordinary tornado warnings urge residents to their basements, but an update to Saturday’s special warning was rewritten to replace that call-to-action advice with instructions to follow evacuation orders.

“Do not go into this area! Life-threatening situation!” stated the warning.

Fire tornadoes in and of themselves are rare; being able to detect them in real time on radar is something new.

Wendell Hohmann is the meteorologist at the Reno office who issued the precedent-setting warning. He described it as a “once-in-a-lifetime, career event.”

“We were just trying to get the message out of the extreme fire behavior from this fire given the rotation and the tornadic potential,” Hohmann said. “We figured we could do a severe [thunderstorm warning], but we decided to do a tornado warning to get [the emergency alert system] and [wireless emergency alerts] to activate.”

It’s the first tornado warning his office has issued since a waterspout touched down on Lake Tahoe in September 2017.

Fire tornadoes are rare, but not unheard of. Increased awareness surrounding their occurrence in recent years suggests they may be more common than originally thought.

The EF3-strength fire tornado associated with the Carr Fire near Redding, Calif., on July 26, 2018, killed a firefighter and damaged high-voltage electrical structures with winds estimated up to 143 mph. Doppler radar also observed a rotational “couplet” in the enormous smoke plume where strong spin was occurring.

That would make it one of California’s strongest tornadoes, and first killer tornado, on record.

Hohmann said he was thinking about the firefighter killed by the Carr fire tornado in 2018 when he issued Saturday’s warning in an effort to raise awareness of the extreme and erratic fire behavior that was occurring.

“Given what happened in California, we knew what these things could do,” he said. “We wanted to get the message out. We could see the [smoke] column clear as day from our office. You could tell this was no usual fire situation. It looked like a volcanic column going up.”

On radar, several of the rotational couplets appeared strong enough to be supportive of not only tornadoes, but potentially borderline significant tornadoes. Significant tornadoes are twisters of EF2 strength or greater on the Enhanced Fujita scale, with winds exceeding 111 mph.

“It was an extraordinary event,” said Nick Nauslar, a meteorologist specializing in fire weather with the National Interagency Coordination Center in Boise, Idaho. “The rotational velocity. … You know that could be an EF1 or EF2 tornado.”

The majority of Saturday’s fire tornadoes appeared to spin clockwise, contrary to how most tornadoes rotate in the northern hemisphere. That indicates more localized mechanisms or subtle features were likely in play, such as surface convergence in the lee of a mountain or the interaction of the nearby landscape.

“One thing we’ve noticed is that sometimes the anticyclonic [clockwise] side can become dominant, and it seems to happen [in wildfire smoke plumes] more often than it does in [rotating supercell thunderstorms]," said Nauslar.

The influence of more regional or nearby conditions adds a new dimension to fire weather forecasting that may in the future allow meteorologists to anticipate fire tornadoes ahead of their development.

The National Weather Service in Reno is hoping to dispatch a survey team to begin the process of investigating and cataloguing the fire tornadoes as soon as it is safe to do so.

The wildfires in California come as a serious heat wave grips the Golden State and much of the West. Records fell across California, including in Sacramento, where the temperature on Saturday hit 111 degrees. Downtown Los Angeles reached 98 degrees, tying a record.

Needles, in California’s southeast desert, soared to 123 degrees, its highest August temperature on record.

On Friday, Oakland hit 100 for the first time on record in August while Phoenix tied its hottest temperature for the month: 117 degrees.

The hot weather pattern even helped fuel a rare complex of severe thunderstorms in the San Francisco Bay area early on Sunday, captivating Californians in an area that doesn’t hear thunder all that often.

Virtually the entire western fifth of the Lower 48 is blanketed beneath heat advisories and warnings on Sunday, except for the high-altitude Sierra Nevada. Dangerous heat indexes, locally in the 120s, can be expected Sunday into early parts of the workweek before the heat tempers a bit.

The heat will also exacerbate ongoing firefighting efforts and make the spread of wildfires a greater concern. And as the climate continues to warm, many meteorologists are worried extreme fire behavior will become more routine.

“It seems like the fire behavior is getting more extreme as the years go by,” said Hohmann. “This is just a subjective feel, but it just seems to me that things are getting drier and hotter on the fire front. You get these unusual bursts of fire spread, extreme fire behavior, it’s crazy. … But this is the first time I had seen it in my backyard.”

Jason Samenow and Andrew Freedman contributed to this report.