LAS VEGAS >>Most of Nevada was under a flash flood watch on Monday with more rain in the forecast as unseasonably cool weather pushed across the region on the heels of one of the state’s hottest July’s ever.

Flash flooding closed some streets in northwest Las Vegas during the Monday morning commute after about an inch of rain fell in an hour on Mount Charleston, washing out several roads overnight.

A flash flood watch was in effect until 9 p.m. Monday in parts of Clark and southern Nye county, and in northern Nevada in parts of Elko, Lander, Eureka and Humboldt counties.

Temperatures were between 10 and 15 degrees cooler than usual across the state, the National Weather Service said.

On Sunday, Death Valley’s high of 89 was the coolest ever for Aug. 3, shattering the old record of 104 set in 1945. It was only the seventh time since 1911 that the temperature there had failed to crack 90.

It was in stark contrast to the unusually warm July in Nevada. Winnemucca — about 160 miles east of Reno — recorded its warmest monthly average temperature on record in July with 77.5 degrees, the weather service said on Monday.

The heavy rains caused the Nevada Department of Transportation to close a stretch of state Highway 159 about 5 miles east of Red Rock Canyon early Monday to clear debris from high waters. More than an inch of rain fell near Mountain Springs Summit between 4 a.m. and 5 a.m., and about a half inch was recorded in the southwest part of Las Vegas Valley.

In addition to road damage in the Mount Charleston area, the service said the rains caused erosion on Rainbow Canyon Boulevard, a landslide on Kyle Canyon Road and washing out Harris Springs Road.

Minor flooding had receded in the metropolitan area by about 7 a.m.