Storms brought a tornado and golf-ball-sized hail to Wyoming that downed power lines, damaged homes and pushed some empty train cars on their sides Thursday, a day after thunderstorms pummeled parts of Wyoming and Colorado with 2-inch hail and heavy rain.

Five structures were heavily damaged by the tornado Thursday, and 10 to 12 other structures also have damage, said Kelly Ruiz of the Wyoming Office of Homeland Security.

One person was treated at a hospital for a cut on the head, said local radio station owner Kent Smith, speaking for the Platte County Sheriff's Office.

A Burlington Northern Santa Fe railroad crew reported the tornado struck a train that had stopped in the Wheatland area due to 55 mph winds and a tornado warning, BNSF spokesman Gus Melonas said. Five empty train cars derailed onto their sides, and another was leaning over, he said. No injuries were reported.

Some power lines also were downed, Ruiz said.

The tornado touched down briefly near Wheatland, north of Cheyenne, in a sparsely populated area, officials said. One of the destroyed homes was vacant, Smith said.

Hail was reported in the Wheatland area and Laramie, National Weather Service meteorologist Tim Trudel said.

The National Weather Service issued a tornado watch for parts of Colorado, Wyoming and Nebraska through Thursday night. Forecasters said thunderstorms that can spawn tornadoes could develop and flooding was possible.

In Colorado, a tornado was spotted near Calhan in El Paso County on Thursday night. Meteorologists were trying to confirm a report of a tornado to the north in Elbert County near Simla. Elbert County officials reported damage to eight houses, including two that were missing roofs and others with broken windows. They also received a report of one minor injury and standing water on two roads, spokeswoman Kara Gerczynski said. Meanwhile 2.5-inch-diameter hail was reported in El Paso County near Peterson Air Force Base.

On Wednesday, preliminary reports indicated about five tornadoes touched down in Colorado, including one near Denver International Airport. No serious damage was reported. Snowplows were called out in Douglas County, south of Denver, to clear hail up to 8 inches deep. About 40 people in Colorado Springs were rescued after cars became submerged in water and hail, including near Citadel mall, firefighters reported.

The rain provided some help to firefighters who fully contained a 227-acre wildfire in northern Colorado, but the weather initially hurt efforts to control a 6,000-acre blaze in Wyoming's Medicine Bow National Forest.

Storms passed close to the Wyoming fire but mostly brought gusty winds that fanned the flames. Rain and hail fell later but didn't make a significant difference, said fire spokeswoman Beth Hermanson.

Kyle Fredin, a meteorologist for the National Weather Service in Denver, said the beginning of June is the peak time for such severe weather in Colorado. Most of the state has been experiencing moderate-to-extreme drought conditions.

"It's game-on for this type of thing," he said.

Rob Cox with the weather service in Cheyenne said hail measuring 2 inches in diameter was reported about 18 miles northeast of the city. Cheyenne and areas to the east received from 1 to 2 inches of rain, he said.

Jim Elias, a city public works director, said the drainage system worked well considering that nearly 2 inches of rain fell in a little more than two hours in some areas.

Cheyenne has spent millions of dollars improving drainage around the city since a flood in 1985 killed 12 people.

Elias said crews were called to areas with deep water but most of the water had gotten into the drainage system and had been carried away.