The National Weather Service said that rain and thunderstorms could continue over the urban corridor until 6 p.m. Rainfall rates of one quarter to three-quarters of an inch per hour were possible and could add to flooding caused by the earlier storm.

The hail piled up 4 inches deep at Elitch Gardens amusement park in downtown Denver, a spokeswoman said.

Drivers were caught in up to 3 feet of water in some intersections, but no

serious injuries were reported, Denver Fire Department spokesman Phil Champagne said.

"It hurt. I probably got bruises. It was huge," said Brazil Redd, 21, of Edgewater, who got caught in the hailstorm. "I got soaked."

She was outside when the rain and hail began, having her car towed away after a hit-and-run accident.

Marty Thrall plodded through a half inch of hail in a short-sleeved T-shirt, shorts and sandals.

"I didn't know it was going to be this icy," he said.

Drivers scurried to get under bridges or into garages. Insurers braced for damage claims, but the dollar value may not be known for a couple of days.

"We're in a wait-and-see mode until we can get claims in and have adjusters look at damage," said Carole Walker, executive director of the Rocky Mountain Insurance Information Association.

"Certainly, we are in hail alley. We get more severe hail here than almost anywhere else on Earth. It's not unusual," she said.

Firefighters responded to an emergency call at 38th Street and Brighton Boulevard near the National Western Complex, and four occupied cars were swamped by flash flooding at Martin Luther King Boulevard and Magnolia Street. Another set of cars was trapped in water at 37th Avenue

Hail began pounding Denver at about 1:30 p.m. on Tuesday, May 29, 2007. (Ken Lyons | The Denver Post)and Columbine Street.

Manhole covers and storm-drain grates were blown out of position by gushing runoff along Champa and Curtis streets near 29th Avenue.

Heavy hail began falling in Jefferson County just after 1 p.m. A five-minute burst of hail - some of it a half-inch in diameter - stripped leaves from trees and coated streets in parts of Golden and Lakewood.

Another severe thunderstorm hovered over central Commerce City.

Streets in downtown Denver took on the look of a snowstorm in January, with white stuff covering the asphalt and tire tracks zigging and zagging down thoroughfares.

The storm moved through the metro area quickly, lasting fewer than 30 minutes.

The Denver Botanic Gardens, nearly in full bloom,

A woman wearing flip-flops walks through a pile of hail after a storm in downtown Denver on Tuesday afternoon, May 29, 2007. (AP Photo/Ed Andrieski)suffered some damage "but not nearly as bad as it could have been," said Dan Johnson, curator of native plants. "The iris and peonies were hit pretty bad," he said, "but they have more buds coming out, so it will be just a temporary setback."

Firefighters in Fort Collins had to douse two house fires caused by lightning within 17 minutes of one another.

The first call came in at 12:40 p.m. about a home in the 6300 block of Treestead Road in south Fort Collins. Damage was limited to a hole in the roof and light smoke damage in the home.

The second blaze, at 12:57 p.m., was in the 5000 block of Foothills Drive, where the roof caught fire. Firefighters rescued a dog, and damage was estimated at $35,000.

Trail Ridge Road in Rocky Mountain National Park, which just opened over the holiday weekend, was closed again by the storm, which triggered a snowslide.

A flood watch is in effect for Cheyenne, Kit Carson and Yuma counties until 6 a.m. Wednesday.

The Associated Press contributed to this report.