More than 3,000 acres (1,200 hectares) of grass and woodland have been consumed since Tuesday when a blaze started just outside Oroville, with authorities telling 13,000 people to leave the area.
The town, near the state capital of Sacramento, is just 23 miles (38 kilometers) from Paradise, a community that was razed in 2018 by the deadliest fire in state history, in which 85 people perished.
Garrett Sjolund, fire chief of Butte County, said the area was under a so-called "red flag warning."
"The conditions out there that are in our county this summer are much different than we've experienced the last two summers," he told reporters.
"The fuels are very dense. Brush is dry, and as you can see, any wind will move a fire out very quickly."
Climate scientists say the western US is undergoing a decades-long aridification as weather patterns change, at least in part because of human-caused global warming.
California suffered around 20 years of drought, but the last two years were relatively mild, with near-record amounts of rain that filled reservoirs and sparked furious growth in forests and grasslands.
However, 2024 is shaping up to be a hot and dry year, and that flora is rapidly drying out, creating plenty of fuel for the wildfires that are a normal part of the ecosystem's natural cycle.
The conditions have left officials warning of potentially devastating blazes waiting to happen, especially if people are careless or negligent with fireworks over the upcoming July 4th Independence Day holiday.
"We've had four fires within the last couple of weeks. This is a bad fire season," said Butte County Sheriff Kory Honea.
"The last thing we need is somebody who's purchased fireworks from a local fire stand going out and doing something stupid. Don't be an idiot."
On Wednesday, around 400 firefighters were attacking the flames on the ground with heavy machinery and by air with planes and helicopters.
Sjolund said that equipment and personnel were arriving from other jurisdictions to reinforce operations.
The National Weather Service warned that temperatures were expected to remain very high, reaching up to 115 Fahrenheit (46 Celsius) in some spots over the coming days.
"An exceptionally dangerous situation is underway as we enter a potentially deadly, historic, and prolonged heat event," the service wrote on social media.
