Relief is expected today from the muggy and variable weather that has plagued the Washington area since the beginning of August. The prediction by the National Weather Service came after heavy downpours yesterday soaked the metropolitan area for the fifth straight day.

A spokesman for the service said that an upper atmosphere cold trough that has caused blackened skies and heavy rains for the last week was expected to move over the Atlantic Ocean overnight, leaving warmer but drier weather here.

Yesterday, though, a series of thunderstorms surged through the District of Columbia at about noon, dropping more than an inch of rain in a two-hour period. The storms temporarily disabled hundreds of autos, flooded dozens of area roads and basements, and caused the cancellation of scores of outdoor activities.

U.S. Park Police reported flooding on Rock Creek Parkway and Independence Avenue. One official said dozens of motorists were stalled in a foot of water for nearly half an hour yesterday on Madison Drive near the Mall.

According to D.C. Police, automobile traffic at the intersection of 15th Street and Constitution Avenue was at a standstill for an hour in nearly two feet of water.

Police jurisdictions, from Montgomery County through the Virginia suburbs, reported an increase of minor traffic accidents due to slick streets and blinding rain, while fire jurisdictions reported minor flooding in many area homes.

In Rockville, water overflowing from a small creek reached the kitchen door of Barbara Streams' house at 410 Horners La. Mrs. Streams estimated that seven feet of water was outside her door, the highest level she has seen all summer.

At 3407 Carlyn Springs Road in Falls Church, Cecelia LaFlower reported that her basement apartment was flooded with waist-high water. LaFlower said she was forced to relocate after several rooms in her apartment became knee-deep in sewage from a backed-up toilet.

In Washington, minor damage was reported at the National Air and Space Museum after rain leaked through the museum roof and soaked a lobby carpet.

The rains forced the cancellation of innumerable picnics, barbecues, softball games and outdoor music concerts. The D.C. Department of Recreation Showmobile, an itinerant music and dance extravaganza, packed up and left a park at Wheeler and Mississippi Roads SE after the grass there was filled with an inch of rain.

On the Mall, a religious conclave of east Indian gurus was postponed, as was a scheduled Jefferson Memorial performance by the U.S. Marine Band.

Yesterday's high temperature was 85 degrees at 11:45 a.m. The National Weather Service expects continued warm weather today, with high temperatures in the upper 80s and a 20 percent chance of thunderstorms.

"What we've had lately is a very shaky situation caused by warm surface airs and the upper-atmosphere cold trough," said a spokesman for the service, referring to the thunderstorms that have dropped nearly 3 1/2 inches of rain in the metropolitan area since Aug. 1. "When those two met, a lot of stuff began to happen."

According to Don Gilman, a long-range forecaster for the service, the weather here for the next 10 days should be better.

"A hot air mass in the midwest should mean a slackening off of the rains in this area," he said.