Indian summer lulled Washington in a warm autumnal embrace yesterday as thousands of workers lingered in dowwtown parks and elsewhere for a last nostalgic rendevous with the season's fading sun.

Technically, it was a day of record-tying warm temperatures and high barometric pressure working their meteorological magic on the city. But for the average mortal Washingtonian, it was a classic hookey-playing-close-the-office-early-let's-go-fishing kind of a day.

At 4 p.m., the temperature hit a comfortable 84 degrees at National Airport, tying the previous record high set for the date in 1920.

The day was the last of a string of warm and generally sunny days here that the National Weather Service said qualify as an Indian summer. It is likely to come to an end today, however, forecasters said, with clouds, lower temperatures and scattered showers taking over.

Today's forecast calls for temperatures in the low 70s and a 70 percent chance of showers and thunderstorms. By the end of the week, temperatures should slide back to seasonally normal levels with highs in the 60s during the day and lows in the 40s at night.

Yesterday's record-tying heat comes on the heels of Washington's freak early autumn snowstorm of Oct. 10, when the thermometer plunged into the mid-30s and heavy wet snow snapped tree limbs and power lines throughout the area, leaving thousands of homes and stores without electricity.

The area remained locked in below-normal cold for several days, and it was not until Oct. 17 that the current spell of Indian summer began and some measure of comfort returned to the city.

An Indian summer is a common, but not automatic, feature of autumn. On Oct. 23 and 26 last year, for example, the area enjoyed a sudden warm spell with record-tying high temperatures. In other years, however, there has not been a distinct Indian summer. Instead, the area has simply slid slowly and unceremoniously from the heat and humidity of summer to the slush and snow of winter.

The National Weather Service defines an Indian summer as a period in mid or late autumn of abnormally warm weather with generally clear but hazy skies and cool nights. In New England, an Indian summer is not considered authentic unless it has been preceded by a killing frost.

Weather service forecaster Gody Rivera said yesterday that the current Indian summer has been caused by a massive stagnant high pressure system extending across much of the Atlantic to the southeastern states. The system has been stationary for almost a week but should start breaking up and moving eastward today, Rivera said.