It's been, in my judgment, a fairly decent Washington winter so far. Translated, that means the snow hasn't plunged too far. And, after obeisance to those spiritual, I voiced thanks during yesterday's icy traffic-snarling blast to those temporal who provided a subway to get me to the office without delay.

That got me to thinking. What kind of weather can we really expect this time of year in Washington? The historical answer: wild swings.

We went back and checked the historic high and low temperatures for the dates bracketing the first week of February. Even knowing that Washington is on the climatological boundary between cold northern and warm southern weather systems, the results were surprising. The spread was 73 degrees from coldest to warmest. The data:. Feb. 1 -- 41 degrees high this year. Historic low, 2 below zero in 1905; historic high, 71 in 1916. Feb. 2 -- 44 degrees. Historic low, 6 above in 1935; high, 67 in 1877. Feb. 3 -- 46 degrees. Historic low, 0 in 1895; high, 65 in 1927. Feb. 4 -- 38 degrees. Historic low, 2 above in 1898; high, 68 in 1883. Feb. 5 -- 53 degrees. Historic low, 2 below in 1918; high, 70 in 1890. Feb. 6 -- 47 degrees. Historic low, 1 above in 1895; high, 69 in 1938.

So why go off to Florida? Or, for that matter, to Vermont? Wet Stuff

Speaking of the weather, and getting back to the present, we present our monthly report of the Potomac River flow. In January, after a previous flood period, the U.S. Geological Survey says the Potomac registered less than half its normal January volume: 3.8 billion gallons averaged daily at Little Falls, just above Washington, compared with a normal average for January of 8.5 billion gallons.

Fresh water flow from all sources into Chesapeake Bay was 34 percent below normal for the month. In the long term, this could disturb the ecology of the bay.

But of somewhat greater concern is the fact that, for the 17th straight month, the water table in northeastern Montgomery County remains 1 1/2 feet below normal -- a matter of concern to regional agriculture. More Wet Stuff

The Bartenders' Ball, sponsored or supported by the people described by its name and by their bosses, is being held tonight at the Sheraton Washington Hotel -- and with an unusual twist.

Those who weave out of the ballroom and need a ride home will be able to get one free by asking the Diamond Cab dispatcher at the hotel's front door. "The only stipulation is that the rider must go straight home," said Peter Alafoganis, a chairman of the ball.

Proceeds will go to 15 deserving charities ranging alphabetically from Big Brothers to the Zacchaeus Soup Kitchen.