Flooding and scattered power failures plagued the Washington area again yesterday as rain fell for the 19th day of the past 26. Forecasters, however, predicted today would bring a brief respite from the foul weather with the reappearance of late-spring blue skies and temperatures in the low 80s.

The canceled baseball games, ruined picnics, water-logged beach excursions, flooded basements and dampened spirits are not over, however. Rain should be back in the area Wednesday and Thursday and the National Weather Service has forecast more gray skies and precipitation for the rest of the month.

The culprit in this month's meteorological mess, according to weathermen, is an errant jet stream. Normally at this time of year the jet stream and its accompanying storm systems are north of here, moving through the upper United States and Canada. This year these strong winds drifted south, causing above-average rainfall and temperatures that have averaged five to six degrees cooler since June 3.

By mid-afternoon yesterday, the area had soaked up more than one inch of rain in a 24-hour period and about 3.5 inches during the first 13 days of the month. The usual average for the entire month of June is 3.8 inches.

The persistent downpour yesterday caused flooding on many secondary roads in Fairfax, Loudoun and Prince William counties, and resulted in stream flood warnings in Montgomery and Frederick counties. Six to eight inches of water covered portions of Rtes. 66 and 50, according to Loudoun County fire department officials.

Electric company officials reported scattered power failures in Prince George's and Fairfax counties and northwest Washington.

For those who planned a day of recreation, yesterday's weather could not have been worse. Many who had flocked to the beaches at Ocean City and Rehoboth for a weekend of sun returned home dejectedly by midday.

More serious was the experience of an unidentified man and woman who chose yesterday of all days to try kayaking on rain-swollen Rock Creek. Their small craft crashed onto some rocks in mid-stream between Military Road and Carter Barron about 7 p.m., stranding them there for more than an hour. They were finally brought to safety by D.C. firemen using a shore-to-shore rope hoist.