OAK CREEK CANYON, Ariz. (AP) — A wind-whipped wildfire in a canyon near Flagstaff dramatically increased in size Wednesday as it sent up choking plumes of smoke, threatened homes and scuttled Memorial Day weekend plans in the popular hiking and camping area.

Hundreds of firefighters poured into northern Arizona to battle the fire between Sedona and Flagstaff, and by Wednesday afternoon, the fire grew to an estimated 7 square miles, or about 4,500 acres. The erratic and gusty winds briefly grounded air tankers that were brought in to fight the fire.

Authorities also warned about 3,200 residents in communities near Flagstaff that they should be ready to evacuate if the fire makes another advance.

Officials are fearful that the fire could be a prelude for what could become a devastating wildfire season amid a drought that has left tinder-dry conditions across the state.

The blaze presented several challenges for firefighters, including steep terrain, thick pine forest, gusting winds and the drought conditions, said Bill Morse, a Flagstaff Fire Department captain and a spokesman for firefighting managers. The winds helped the fire race 2,000 feet up the canyon and to a plateau area.

The fire broke out at the start of the tourist season and closed the main road between Sedona and Flagstaff — two cities that attract visitors in summer months. The fire is burning near Slide Rock State Park, a popular recreation area because of its natural rock water slides.

Sophie Lwin, of Peoria, said she had relatives from the Los Angeles area coming in for a weekend at the Butterfly Garden Inn, which had to evacuate because of the fire. She said the area is her favorite destination, and she and her husband visit at least five times a year.

“It’s Memorial Day weekend. It’s going to be so hard and so expensive to get anything anywhere else,” she said.

About 500 firefighters and other personnel are already assigned to the fire, including 15 Hotshot crews.

But windy conditions forced firefighters to temporarily halt air resources such as retardant. They were flying again Wednesday evening.

Crews were focused on keeping the fire west of a highway near threatened homes. There were no reports so far of injuries or structures burned.

The cause of the fire wasn’t known, but authorities believe it was human-caused.

The fire forced the evacuations of 100 businesses and homes in a 2-mile stretch north of the state park, and 15 people stayed at a shelter in Flagstaff. About 3,200 people in the communities of Kachina Village and Forest Highlands were told that they need to be ready to evacuate.

“As you can see, we are dealing with some pretty extraordinary circumstances with this fire. I want to reiterate that you basically have received your pre-evacuation notice. This is your time to get ready,” said Robert Rowley, emergency manager for Coconino County.

The fire comes less than a year after a blaze in nearby Prescott killed 19 firefighters who were part of a Hotshot crew.

As the latest fire moved up the canyon’s steep walls, it sent up large amounts of smoke and ash and created hazy conditions in Flagstaff, about 15 miles away.

But Morse said calming fire conditions in Southern California have freed up extra crews to fight the Arizona blaze.

The evacuees included Nathan and Mickella Westerfield, honeymooners from Phoenix who arrived at a campground in the canyon Tuesday afternoon. They were headed into Sedona for dinner when they passed the fire, which was burning in a valley visible from the highway.

As other passers-by stopped to take pictures of the fire, a firefighter told the couple they couldn’t return to their campground to retrieve their newly purchased camping gear and other belongings, Nathan Westerfield said.

“He told us, ‘no, we’re evacuating,’” he said. “We literally have the clothes on our backs.”

Red Cross spokeswoman Trudy Thompson Rice said most of the people who stayed at the shelter at a Flagstaff school Tuesday night were campers. The Westerfields were among those who spent the night.

Three other active fires were reported Wednesday around the state, including a 150-acre forest fire east of Payson in northern Arizona.

Crews also were battling a 200-acre wildfire on the Tohono O’odham Indian Reservation southwest of Tucson and a 450-acre brush fire on the Babacomari Ranch in the southern Arizona town of Sonoita.