SAN FRANCISCO >> Red flag warnings of extreme fire danger subsided, but warm and dry weather continued to challenge firefighters battling more than two dozen blazes across California today as the state approaches an astonishing milestone: 4 million acres burned by wildfires this year.

The state is about 20,000 acres from reaching the unprecedented figure, fire officials said. Meanwhile, two major fires that have killed four people and incinerated hundreds of homes in the wine country and the far north continued to burn.

Powerful winds that had been expected to drive flames since Wednesday hadn’t materialized, and warnings of extreme fire danger for hot, dry and gusty weather expired Saturday morning as a layer of fog rolled in.

But with California a tinderbox of dead trees and dried brush after weeks of scorching weather and years of drought, fires could explode in rural areas, grasslands and dense forest even without the push of winds.

Above-normal temperatures and low humidity persisted today, heightening the fire danger.

“It just leaves us kind of nervous that we’re not out of the woods yet when it comes to what might happen in California,” said Jonathan Cox, a deputy chief with the California Department of Forestry and Fire Protection, known as Cal Fire.

A cooling trend is expected to slowly begin on Sunday. Long-range forecast models hinted at the possibility of rain early next week.

The easing winds proved a mixed blessing at the Glass Fire in Sonoma and Napa counties. Although the fire raged on, crews got a break as they struggled to keep flames from jumping containment lines and renewing their march toward scenic communities.

“The good news is that with the lack of wind, we didn’t have continued control issues,” said Ben Nicholls, a Cal Fire division chief.

“However,” he added, “due to that lack of wind, the smoke has stayed in place” and hindered aircraft from attacking the blaze.

Evacuation orders for many of the 5,000 residents of Calistoga were reduced Friday to warnings, although trees and some homes on the town borders were burning.

The fire, which had destroyed about 600 homes and other buildings, still threatened around 29,000 homes.

The fire had burned 97.4 square miles (252 square kilometers) and was only 10% contained.

In Shasta County in the north end of the state, the Zogg Fire that began Sunday has killed four people and destroyed nearly 180 structures. Containment slightly grew to 57% contained.

Altogether, wildfires have killed 31 people and destroyed 8,200 structures in California this year. Many of the largest fires were started by lightning strikes in mid-August and most of the destroyed acreage has come since then.

Some 17,000 firefighters are still battling nearly two dozen major blazes.

Numerous studies have linked bigger wildfires in the U.S. to climate change from the burning of coal, oil and gas. Scientists say climate change has made California much drier, meaning trees and other plants are more flammable.