CASTLE ROCK, Colo. -- A blast of heavy rain washed out a few driveways and roads in eastern Colorado and triggered a mudslide in the mountains Sunday, signaling what could be the beginning of monsoon season, the National Weather Service said.

Radar estimates suggested 5 inches of rain fell in parts of eastern Douglas County and western Elbert County south of Denver within about two hours Sunday afternoon, but actual reports were lower, according to the National Weather Service.

In the eastern metro area heavy rain flooded Gun Club Road between Alameda and Mississippi Avenues with up to 3 feet of water. The road was closed from late afternoon until late evening. One to two inches of rain fell in a line from northern Douglas County to eastern Aurora within a period of 90 minutes.

A mudslide closed Red Mountain Pass on U.S. Highway 550 between Ouray and Silverton for an hour, said Mark Aultman of the state transportation department. The weather service reported slow moving thunderstorms in the area.

Without heavy winds to push the thunderstorms along in eastern Colorado, 2.5 inches fell in less than two hours near Kiowa in Elbert County. North of Akron, almost 2 inches fell in a little over an hour, and south of Fleming in northeast Colorado, 1.1 inches fell within 45 minutes.

In Washington County in northeast Colorado, water had collected across U.S. 6 by Prewitt Reservoir, a county sheriff's dispatcher said.

The monsoons are the result of Pacific moisture from Mexico that travels through Arizona up to Colorado. The monsoon season normally doesn't begin until mid-July but weather experts said that it began early this summer.

To see all the precipitation reports from Sunday's storms, check out the CoCoRaHS maps.