They were told weather will play a big role in battling the blaze on Sunday.

Park Rangers said wind conditions would be calm early in the day but would pick up again in the evening.

The gusts could be as powerful as they were Friday night when the fire really picked up.

The Fern Lake Fire doubled in size Saturday, but officials are still "cautiously optimistic" as national crews prepare take part in the operations.

One private cabin was lost in the fire that grew rapidly Friday night and prompted evacuations. No injuries have been reported.

As of Saturday evening, the fire was at more than 3,500 acres with no estimation on containment. More than 150firefighters are fighting the fire on the ground and will monitor its progress overnight Saturday.

The east side of Rocky Mountain National Park is closed, but the Fall River Visitor Center remains open.

The fire more than doubled in size and spread roughly 3 miles in just 35 minutes early Saturday morning.

Fire crews say they're cautiously optimistic for the fire since winds were not as extreme Saturday as they were Friday night.

The sheriff's department says 1,100 emergency notifications were sent to residents Friday night as the fire grew.

Approximately 681 of those contacts were still evacuated along Highway 66 Saturday night.

Authorities have scheduled an evacuee meeting at the Estes Park High School for 10 a.m. Sunday.

The Highway 66 corridor, including all adjacent streets, remains in evacuation. Power is still on in the Highway 66 corridor.

Residents of High Drive and adjacent streets are now on pre-evacuation notice. The residents in this area may return home, presenting identification to law enforcement at the High Drive road block. No others will be allowed in the area.

Residents who were evacuated Saturday from the west side of Marys Lake Road and all adjacent streets are now allowed to return home and are on pre-evacuation notices. Access to the neighborhood is unrestricted.

Evacuees are asked to go to Estes Park High School at 1600 Manford Ave. All public events at the Estes Park High School have been canceled Saturday.

The evacuation center will transition from the Estes Park High School to the Mountain View Bible Fellowship at 5 p.m. on Sunday, Dec. 2. Mountain View Bible Fellowship is located at 1575 South Saint Vrain Avenue (CO Highway 7), at the corner of Peak View Drive.

Large animals may be taken to the Stanley Park Fairgrounds 1209 Manford Ave.

Campers in the Moraine Park campground reported seeing flames in the meadow. They told 9NEWS the fire grew larger just after 2 a.m. Saturday. As of 10 a.m., the fire had not crossed Bear Lake Road.

Fire information officer Traci Weaver told 9NEWS in a live interview it's good news the fire has not crossed Bear Lake Road, and crews are hoping to keep that from happening. The fire remains inside Rocky Mountain National Park.

Weaver also told 9NEWS that winds have died down Saturday morning after driving the fire during the night, but there is still obviously significant concern about the fire's behavior. Officials are concerned about high winds Sunday evening.

Fire updates on InciWeb here:

Wildfires during the colder months in Colorado are less common than they are in the spring and summer, but the unusually dry pattern this year has created dangerous fire conditions, even as we enter December.

The cause of the wildfire, which began Oct. 9, is still under investigation. Weaver says it may have been human-caused from an escaped campfire.

Stay tuned to the networks of 9NEWS for the latest information.

Map of Fern Lake Fire evacuation area:

View Approximate evacuation area for Fern Lake Fire in a larger map