Thousands of firefighters across 10 states west of the Mississippi River are battling massive fires that have destroyed homes and displaced hundreds of people and, in some cases, continue to burn out of control.

The unusual amounts of snowfall and rain across the West this last winter helped facilitate tall grass and more vegetation — creating conducive conditions for large fires once the hot and humid months of summer rolled around. Lightning strikes have sparked many of the fires and some blazes have been burning for weeks.

Wildfires remain active in Alaska, California, Colorado, Idaho, Montana, Nevada, Oregon, Texas, Washington and Wyoming, according to the National Interagency Fire Center.

“When wildfires threaten resources, that’s when firefighters will do everything they can to minimize the threat and go after the fires to put them out,” said Robyn Broyles, spokeswoman for the National Interagency Fire Center. “At the same time, wildfires play an important role to helping restore the balance of our ecosystem. In that case, firefighters supervise it.”

There are currently 40 uncontained large fires burning across the nation. So far this year, the entire United States has experienced 36,182 large fires, which burned nearly 5 million acres — almost the size of Minnesota, Broyles said.

Here are a few key states where crews are fighting flames.

Montana

A plane drops retardant on a wildfire near the historic mining town of Landusky, south of the Fort Belknap Indian Reservation in north-central Montana. (Meg Oliphant / Associated Press)

The largest of 16 wildfires that have engulfed parts of Montana is burning in Garfield County, where 657 firefighters are on the fire lines, according to the National Interagency Fire Center. Crews from 23 states have joined local firefighters to battle the fire, according to Ray Hageman, Garfield County fire warden.

“Some people are ecstatic that people are here to help them,” Hageman said of county residents. “But others just lost their entire livelihood. It’s rough.”

Twelves homes were destroyed and about six ranches severely damaged. Still, about 99% of livestock in the county has been taken out of harm’s way, and though some people experienced heat exhaustion and heat strokes in recent days, there have been no reports of major injuries, he said.

Montana Gov. Steve Bullock on Monday declared a fire emergency in the state after more than 250,000 acres of the Lodgepole Complex fire burned. That fire started on July 19 following a lightning storm.

“Montana is racing extreme fire conditions. Our top priority is ensuring the safety of Montanans, their property and our communities,” Bullock said in a statement Monday. “As firefighters battle blazes across the state, Montanans must stay vigilant about active fires in their area … and prevent any actions that might spark new fires.”

Nevada

Crews work to protect a home site as they battle a wildfire along Pyramid Highway near Reno, Nev. (Jason Bean / Associated Press)

At least seven active wildfires are burning across different parts of Nevada, the National Interagency Fire Center said.

In Douglas County, which borders California near Lake Tahoe, the wildfire sparked by lightning storms threatened structures and led to evacuation orders that were lifted Tuesday after favorable weather slowed the fire, according to the Sierra Front Wildfire Cooperators, while some roads remained closed.

As of Wednesday, 4,651 acres have burned in the county.

Oregon

An Aug. 5, 2015, wildfire consumes a juniper tree as firefighters let it march down to the Columbia River near the Oregon border. (Don Ryan / Associated Press)

There are six active wildfires currently burning through different parts of Oregon.

One of the larger blazes is the Whitewater Fire in the Mt. Jefferson Wilderness Area.

The fire doesn’t present an immediate danger to private property because it is mainly burning in the wilderness. But the area is a popular destination for hikers and at least four hiking trails remain closed.

Wyoming

Jamie Larsen uses a fire wand during a prescribed burn in the North Fork Corridor of the Shoshone National Forest in Wyoming on Oct. 14, 2005. (Justin Lessman / Associated Press)

Firefighters in Wyoming are battling two active blazes in the state.

The Keystone Fire in Albany County, which started in early July, has burned 2,527 acres and is 75% contained. On Tuesday, crews were able to reopen closed roads.

“Thanks to the hard work and diligence of the crews, we are nearly complete with the work on the contingency lines along roads,” incident commander John Markalunas said in a statement Wednesday. He also warned that the fire is still on the move. “It’s possible that this fire will continue to ebb and flow for quite a while,” he said.

The second active wildfire in Wyoming is called the June fire, which began July 18 in Shoshone National Forest. The fire has burned 1,938 acres and is 29% contained.

California

Fire climbs up a hill as the northern front of the Detwiler wildfire burns outside of Coulterville, Calif., on July 20. (Marcus Yam / Los Angeles Times)

Officials in California continue to battle a large wildfire near Yosemite National Park . The Detwiler fire has burned 80,250 acres and was 65% contained as of Tuesday, according to the California Department of Forestry and Fire Protection.

The fire began July 16, prompting officials to order mandatory evacuations. Many of the evacuation orders were lifted Friday and Sunday, and residents were able to return home. The fire destroyed 120 structures, including 60 homes, according to officials.

Support our journalism Please consider subscribing today to support stories like this one. Already a subscriber? Your support makes our work possible. Thank you. Get full access to our signature journalism for just 99 cents for the first four weeks.

melissa.etehad@latimes.com

Twitter: @melissaetehad