"The western edge of fire continued to challenge crews yesterday evening", Cal Fire said Wednesday.
The River Fire is 35,278 acres and 50 percent contained.
"We are making headway and we are feeling optimistic if we can just get a change in the weather", said Cal Fire spokesperson Sean Kavanaugh.
The destructive Carr Fire may have caused some to bend, but when we stand together, we will never break.
Covelo is a highly rural area in northern Mendocino County, east of Highway 101.
To the southwest of the Carr Fire, more than 3,000 firefighters were battling the 95,000-acre Medocino Complex, made up of the Ranch and River fires that have destroyed seven homes and forced thousands to evacuate.
The Carr Fire was one of eight large wildfires burning in the state and 93 burning in the United States, mostly in the West, according to the National Interagency Fire Center.
Of the 20 people reported missing as of Monday, all have now been accounted for.
There are 4,271 firefighters battling the blaze, as well as 369 fire engines, 69 fire crews, 17 helicopters, 125 bulldozers and 84 water trucks.
On Thursday, Cal Fire and the National Weather Service said a survey of last week's damage shows the fire itself created wind speeds of 143 miles per hour.
At a separate news conference on Wednesday, Governor Jerry Brown said the Carr Fire typified a "new normal" authorities are encountering, as large, extremely intense and swiftly spreading wildfires occur more often over a longer fire season.
And here's a new couple to coo over, courtesy of the Grass Valley Fire Service in the Californian city of Sacramento, who were working to tame fires raging in the suburb of Redding yesterday.
The fire is believed to have been started by a malfunctioning vehicle on July 23.
Map showing the perimeter, in red, of the Mendocino Complex of Fires at 11:10 p.m. MDT, August 1, 2018. The weather isn't helping: low humidity, winds, and dry conditions are challenging firefighting efforts.