10:37 a.m. PDT August 5, 2021
Fire officials said in a briefing Wednesday evening that the River Fire west of Colfax, California had damaged or destroyed approximately 35 to 40 structures, but that number is preliminary and could change. Approximately 4,000 structures were threatened as of Wednesday evening.
The fire started at about 2 p.m. Wednesday and had spread for more than four miles when it was mapped at 7:20 p.m. that night. (see map above) Thursday morning CAL FIRE was calling it 2,400 acres.
The south end of the fire generally followed the Bear River drainage which comes out of Rollins Reservoir, then continued to the north-northeast as it spread to the Chicago Park area on Highway 174.
In an 8 p.m. briefing on Wednesday law enforcement officials said 2,400 people were under an evacuation order in Placer County. There were 4,200 under either evacuation orders or warnings in Nevada County.
The fire was pushed Wednesday afternoon by 5 to 8 mph winds gusting at 12 to 17 mph out of the south, southwest, and west while the humidity was in the teens and the temperature 95 degrees. The very dry fuels were receptive to burning embers that started numerous spot fires which burned together resulting in “area ignition”, as described in a briefing Wednesday evening.
Similar to Wednesday, on Thursday the Colfax area is surrounded by, but not officially within, a Red Flag Warning. The forecast for Thursday is for 85 degrees, 14 percent RH, and 8 to 10 mph southwest winds. On Friday it will be warmer (95 degrees) and drier with 9 mph winds out of the west.