A rare fire tornado – or “firenado” – warning has been issued over the weekend in California due to wildfires burning near the Nevada border.

The Loyalton fire, named due to its proximity to the city, has prompted evacuations and jumped a highway on Saturday (15th August), forcing firefighters to protect drivers who tried to avoid the flames.

The National Weather Service (NWS) based in the Nevada city of Reno tweeted that the “extreme fire behaviour” was expected to continue and a fire tornado could follow.

The NWS defines a “firenado” as an “extreme weather phenomenon that can occur with rotating fire columns” and erupts when rising heat from a fire is caught by gusts of wind that change direction, similar to a traditional tornado. It ultimately makes for particularly dangerous conditions as winds combine with smoke plumes.

The Loyalton fire started in Sierra County in the Tahoe National Forest early on Saturday (15th August) and by 5pm, it was estimated to have grown to 20,000 acres and was only 5% contained as it spread toward Reno.

Video captured by firefighters showed the flame burning towards the Interstate-395 highway. The Truckee Meadows Fire and Rescue department tweeted about a “close call” with cars that were left “stuck on the road” as the fire jumped the highway.

John Mittelstadt, a meteorologist at the NWS, told NBC News the “erratic” nature of the wildfires made their trajectory difficult to predict.

The warning came as firefighters also battled at least five wildfires in Colorado – one of which was reportedly the largest in the state’s history.

As of Saturday night, firefighters were dealing with extremely challenging conditions, including hot temperatures, some difficult terrain and highly flammable fuel.

The wildfires in California and Colorado have been put down to a multi-day heatwave across much of the western US, and Mr Mittelstadt said conditions such as these could lead to more “firenados” in future.

He said: “These conditions can lead to more firenados for sure. Everyone need to be very alert and very careful not to create any sparks so that we can avoid any human-caused fires.”