Mid-November weather is making an appearance here in the early part of October with high temperatures reaching only into the 50s, according to the National Weather Service.

The jet stream has dipped far south, bringing the bulk of the eastern states unseasonably cool temperatures, said meteorologist Frank Rosenstein. Normally, mercury readings in the low 70s spare the use of thermal underwear and heavy jackets this time of year.

Steady rain fell over the area yesterday, with National Airport recording nearly a half-inch of precipitation. The heaviest rain fell between 5 and 7 p.m., Rosenstein said. There were no reports of significant flooding.

Rosenstein predicted scattered frost in the far northern and western suburbs tonight and advised residents there to bring in house plants. Overnight low temperatures tonight are expected to range from the mid- to upper 30s in the suburbs and to the low 40s in the District. Weekend temperatures are averaging 15 degrees below normal, officials said.

The record low temperature for Oct. 4 in Washington is 34 degrees, set in 1974. Dulles International Airport's low temperature record also was set in 1974, when its mercury dipped to 24 degrees. National Weather Service officials said there is little chance that those records will be broken tonight.

Rosenstein says that warmer air should move into the area beginning tomorrow. The next temperature dip is expected at midweek, likely bringing rain. "There's a cold front coming in late Tuesday, but it shouldn't be quite this cold," Rosenstein said. He said that high temperatures on Thursday and Friday should reach the 60s.

Weather stations from Norfolk to Wilmington, Del., reported thunder during yesterday's rain. Locally, thunder was reported at National Airport, Baltimore and Fort Meade.

The jet stream can be blamed for the blustery change. The stream has dipped from the western Great Lakes to Georgia. Atlanta and Athens, Ga., reported temperatures in the mid- to upper 50s.

Other parts of the country faced strange temperatures for this time of year. The mercury dipped to 31 degrees at Chicago's O'Hare International Airport, while the thermometer in downtown Los Angeles soared to 108, breaking the record of 102, which was set 102 years ago.