Popular areas in Yellowstone and Grand Teton national parks were welcoming tourists Thursday for the 100th anniversary of the National Park Service, but a wildfire forced some people to drive a little farther than they expected to get to the festivities.

The blaze in Grand Teton National Park shut down a route leading to Yellowstone's South Entrance, so visitors coming from the south through Wyoming will have to take an hourlong detour into Idaho.

Four other entrances to Yellowstone are open, and once inside the world's first national park, visitors won't notice much is unusual other than a smoky haze in some parts of the sprawling park.

"The park attractions and the events scheduled are going off as planned," Yellowstone fire spokesman Bill Swartley said. "There is no impact from the fire that is affecting those events, the centennial events, through the weekend."

They include a visit Thursday evening by U.S. Interior Secretary Sally Jewell at the North Entrance.

The only restriction for visitors inside Yellowstone is the road leading to the south exit has been blocked off at Lewis Lake because of the closure, Swartley said.

Four fires also are burning inside Yellowstone, the biggest spanning about 47 square miles. But cooler, damper weather has slowed the flames, Swartley said.

"There's no threat to park visitors; there's very minimal fire behavior today," he said Thursday. "With the weather conditions prevailing today and tomorrow, the fire is just kind of bedding down."

Julie Guardado of Sacramento, California, and her boyfriend were visiting Yellowstone this week as part of a cross-country trip. They decided to leave Yellowstone a day early over fears of more road closures.

"When we were driving around Yellowstone, we could just see fire around the mountains," Guardado said Wednesday. "Our car still smells like smoke."

Though, she said, "even with the smoke, it was still pretty amazing."

It's a different story for Yellowstone's southern neighbor, where the wildfire in Grand Teton has burned about 19 square miles since lightning sparked it last month.

A lodge and cabin operation and several campgrounds have been evacuated, and a 10-mile stretch of U.S. 89/191/287 leading to Yellowstone has been closed since Monday. No buildings have been lost.

Firefighters have been trying to douse the fire near the highway, but the flames are still intense and the highway will likely stay closed through the weekend, when admission to all national parks is free, fire spokeswoman Karen Miranda said.

"We haven't gotten a break in the weather yet that we've needed," Miranda said. "We're even having difficulty keeping that road open for fire traffic. ... So it is a dangerous condition on that road."

Travelers coming from the south via the popular Jackson Hole area can still access Yellowstone through Idaho and the West Entrance. The detour adds a little over an hour to the drive to Old Faithful.

Grand Teton park and the Wyoming Department of Transportation have posted signs warning drivers of the closure. Grand Teton also is handing out notices and maps of the detour to Yellowstone.

Other wildfires are burning across the West, chasing hundreds of people from their homes and closing popular tourist attraction Hearst Castle in California and destroying homes in Washington state and elsewhere.