At least 1,000 homes have been destroyed and hundreds more are being threatened, Cal Fire says.
Cal Fire says that over 1,000 firefighters are battling this blaze but their focus is on evacuating residents.
PHOTOS: Fire crews battle 10,000 acre Valley Fire in Lake County
The communities of Cobb and Middletown are burning so fast that it is challenging firefighters' ability to warn residents of the danger.
Bay Area Air Quality Management District spokesperson Aaron Richardson said there is no serious health danger from the fire, but people should take common sense precautions if they smell smoke and avoid vigorous outdoor exercise.
Richardson said the air quality will not rise to the level of being unhealthy Sunday because of the strong sea breezes that are helping to clear some of the smoke.
Just In - The #ValleyFire in Lake County is now estimated to have burned 40,000 acres.— CAL FIRE PIO Berlant (@CALFIRE_PIO) September 13, 2015
The Valley Fire has hit Middletown. A school and several homes have been destroyed.— Sergio Quintana (@svqjournalist) September 13, 2015
Extraordinary video from the community of Middletown shows house upon house burning, all you can hear is the crackling of the flames.
We won't know the extent of the damage in Middletown until later Sunday, but it is definitely substantial.
We've received word that the flames have destroyed at least one school -- Middletown Christian School, a small private school that serves students from kindergarten through high school.
Evacuation centers are set up at the Kelseyville Presbyterian Church, Kelseyville High School, and the Calistoga Fair Grounds. The Red Cross shelter is in place for the thousands that have been evacuated. Some 500 people sent the night at the Calistoga Fair Grounds.
Many are sleeping in cots and others are in their cars and tents. The fire has not slowed. We have not received any word yet about how many buildings have been lost.
The communities of Cobb, Middletown and Hidden Valley have suffered extensive damage.
A lot of people are making their way to the evacuation center after spending the night on side roads escaping the fire.
One evacuee, who worked for the forest service clearing fire lines for years, had the best candid description of the Valley Fire. "It was one of the worst things I've ever seen. It looked like you don't want to visit Hell, you were nearly in it," Roger said.
Sue Hamilton lives on West Road in Milton and she came down Highway 29 within the last hour. "Nothing but fire and ash. The ash is so thick you can't even imagine. It's like a movie, a horrible movie."
Hamilton says she has never been without a home and this is devastating for her.
The destruction of the fire cannot be overemphasized.
Many houses were lost, some are spared. At this point Cal Fire is just trying to get people out and protect as many homes as they can. We have not been given any official count related to structures lost.
We're hearing from evacuees that gas stations in Cobb Mountain and Hidden Valley caught fire and exploded as well as propane tanks in Middletown.
Evacuees are getting calls from people who are still in Lake County and the fire's path is taking many turns.
Cal Fire PIO Daniel Berlant spoke with ABC7 News about what to expect Sunday in the fire zone.
Berlant said he hopes for the best but cautioned against any ideas of a quick result. "We're hoping that if the winds do die down just a little bit, if we continue to see cooler temperatures, then we'll be able to really make some good progress to get ahead of this fire. But as we've seen from fire after fire, it's taken days and days and days of hard, tireless work to try and slow down a fire like this. So there may be more communities in the near future and that's what we'll be working with the sheriff's department to try and do as much as we can to those residents if this fire does change direction or does grow in a different, towards a different community."
Additional Mandatory Evacs on #ValleyFire in Lake Co. From Hwy 29 & Hwy 175 south to Seigler Canyon Road, along the south side of Hwy 29.— CAL FIRE PIO Berlant (@CALFIRE_PIO) September 13, 2015
The Lake County Sheriff's Office and Cal Fire have issued a mandatory evacuation orders for the following:
Hwy 29 (Kelseyville) at Hwy 175 south on Hwy 175 towards Cobb, Red Hills Road to Hwy 29, Hwy 29 X Hwy 175 south to Seigler Canyon Road (south side of Hwy 29), Hwy 29 Tubbs Lane (Calistoga, Napa County) to Hwy 29/Hwy 53 (Lower Lake, Lake County) Butts Canyon Road to Napa County Line, including Berreyssa Estates, Butts Canyon Road to Pope Valley. Communities of Cobb, Seigler Canyon, Loch Lomond, Middletown and Hidden Valley Lakes.
New Evacs: Point Lakeview to Soda Bay (Hwy 281)
Hwy 29 X Bottle Rock, Hwy 29 X Hwy 175 (Kelseyville), Hwy 29 X Red Hills Road, Hwy 29 X Seiglar Canyon Road and Hwy 29 from Hwy 2
Livermore Road, Summit Lake Road and north of the community of Angwin. Clearlake Riviera and Riviera West.
In response to the Valley Fire that erupted in Lake County on Saturday afternoon, American Red Cross local disaster workers have opened two shelters: Kelseyville High School at 5480 Main Street in Kelseyville and Napa County Fairgrounds at 1435 N. Oak Street in Calistoga, CA.
At the fairgrounds, they have partnered with Petaluma Animal Services to care for the evacuated pets and animals. There is also a shelter operated by Lake County at the Clearlake Senior Center at 3245 Bowers Avenue in Clearlake.
The shelters are providing immediate needs of those affected, including a safe place to stay, food (dinner, snacks), water, medicines and health services, cleaning supplies, emotional support and other support resources. Impacted residents are welcome to stop by during the day even if they choose to spend the night elsewhere.
Explosions from propane tanks, homes on fire, and Main Street in Middletown in flames. It's a terrible night in Lake County.— Sergio Quintana (@svqjournalist) September 13, 2015
Middletown was where evacuees escaped to for Wragg & Rocky fires earlier this summer. Now it's hit by Valley Fire. pic.twitter.com/MAURjuQYaj— Sergio Quintana (@svqjournalist) September 13, 2015
Middletown in Lake County is now under a mandatory evacuation due to the #ValleyFire. Hwy 29 now closed at Lower Lake to Middletown.— CAL FIRE PIO Berlant (@CALFIRE_PIO) September 13, 2015
Bob Rider is one of those evacuees who shot video on his phone after he got out. He told ABC7 News he, his wife, three young boys and dog "ran for their lives" from their home in Hidden Valley Lake.
"The sound of this fire was that of a jet plane in flight. You could see fire advancing. It was incredible. We weren't evacuating carefully and cautiously, we were fleeing," he said.
Rider says they only had time to grab a couple important items before loading up and leaving.
He believes his home and photography business have been destroyed.
Light rain falling at Napa Co. Fairgrounds where hundreds of Valley Fire evacuees are getting food & shelter. pic.twitter.com/sOtPB3wSy9— Cbarnard (@CornellBarnard) September 13, 2015
Four firefighters, among the first on the scene in Lake County, needed to be rescued after being trapped by the flames.
They belong to a helicopter crew that gets flown into the most dangerous areas to try to stop the flames.
All of them suffered second-degree burns.
"These kind of events are very unusual. They don't occur very often. So when they do, obviously we go in and we investigate, try to figure out what happened. Especially in this situation, so we can prevent of create training so that it would never occur again," Lynne Tolmachoff said.
"When the fire is on and you have to make life or death situations, it's very traumatic to the firefighters," Mike Lopez said.
Medics rushed all four injured firefighters to UC Davis Medical Center in Sacramento.
Other firefighters have stopped by the trauma center near the state capitol to check on them and their families.
The president of CAL FIRE Local 2881, tweeted that he visited the for injured firefighters and said they are all expected to make full recovery.
Update on the 4 burned firefighters from the #ValleyFire. All suffered 2nd degree burns and are in stable condition at UC Davis Medical— CAL FIRE PIO Berlant (@CALFIRE_PIO) September 13, 2015
Visited our 4 injuries Firefighters from LNU at UC Davis Burn Unit. All expected to make full recovery!!— Mike Lopez (@LopezCptmlo) September 13, 2015
4 Firefighters injured in Lake Co. airlifted to UC Davis Med Cntr in Sac with 2nd degree burns are doing well. pic.twitter.com/68w34sPvFm— Sergio Quintana (@svqjournalist) September 13, 2015