By Sunday afternoon, just moving along the C&O Canal towpath without a collision was a challenge. In the inlets along the Chesapeake Bay, open water was fast becoming a luxury. And the fishing lines dangling in the Potomac began snaring each other as often as they snared fish.

The cause? The latest in a string of warm, dry days that have prompted tens of thousands of Washingtonians to head for the outdoors - even if they have to trip over each other getting there.

With unusual rapidity for this time of the year, the grass covering Farragut Square has been disappearing as nearby offices disgorge workers in search of sunshine at lunchtime. Meanwhile, on the weekends, parks have become so full that fistfights have occassionally erupted between rival claimants to picnic tables.

"Once the weather turns nice, but before the beaches have opened, there's a very unusually high demand on the parks and the green space," explained Inspector Hugh Groves of the Park Police. "It's too warm - it's too pleasant - to stay home."

This year that normal human urge for the outdoors has been heightened by the fall-like weather, with daytime highs slipping up into the 70s and 80s while nighttime lows drop down to the crisp, easy-sleeping range of the high 40s and low 50s.

The reason for this overwhelmingly pleasant period goes back to those same upper-level air currents that brought the area its coldest weather in decades a few months ago. A mile or two above us, the air currents have continued their aberrations, bringing a steady flow of dry northwesterly air at a time when humidity is usually beginning to dampen the human outdoor urge.

"It's a very large departure from the usual conditions . . . but I wouldn't say it's natural," said Bob Dickson, a long-range forecast specialist for the National Oceanographic and Atmospheric Administration.

"The temperatures have actually been averaging a little above normal . . . but the difference has been those comfortable morning temperatures; the dry air cools down faster when the sun is down and heats up faster.

The dryness that makes the weather so tempting to wander in, however, is beginning to worry the people who watch the weather most closely: the farmers whose corps are at a tender stage, and the engineers who monitor the draining of the Potomac into our household taps.

According to Charles McClurg, a vegetable specialist at the University of Maryland's Agricultural Extension Service, farms on the Eastern Shore have suffered considerable damage from the sand, which is blown out of the dry soil and into the delicate plants stems.

"The lack of rainfall dries up the soil and the wind blows a lot of sand up onto the crops - it does a lot of damage to small plants," McClurg explained.

Those winds recently killed a lot of field of canteloupe," he added. "They injured a lot of tomatoes."

According to Dickson, rainfall since spring began on March 21 has been about 10 per cent below normal. However, he said that during the next month the humidity and precipitation should return.

In the meanwhile, however, area residents are taking to the parks and the waters to stretch their muscles and their imaginations, and sometimes, the tempers of those around them.

At Great Falls park in Maryland this Sunday, more than 10,000 people came to get a bit of relaxation. Some never got it, as police shut off the parking area for a brief period in the afternoon.

According to Park Service Ranger Jim Martin, one man in his 40s dislocated a shoulder in a fall from his bicycle as he tried to negotiate twopath traffic.

Inspector Hugh Groves of the Park Service police added that sudden confrontations between families holding a permit for a park picnic table and the family already occupying the table in question "have resulted in fisticuffs once in a while."

Out on the Chesapeake Bay in the past week, Coast Guard boats came to the assistance of 65 boats in distress, as compared to 47 the week before, according to Lt. Norman Robb of the Coast Guard's Baltimore station.

Coast Guardsman Clayton Keith of the Annapolis station added, "The good weather means there are more boats out; so more of them run aground, more run out of gas, and more don't get back on time. The sailboats can't get out of the way of powerboats, the powerboats can't get out of the way of sailboats."

Keith estimated that the nautical traffic in his area is up 15 or 20 per cent from the year before.