Yesterday was National Tenants' Day in Washington, a chance for apartment dwellers around the nation to demonstrate in support of tenants' rights.

More than 20 organizations were listed as sponsors of a march on the Captitol to signal the "birth of the national tenants movement."

March organizers promised 7,000 marchers and obtained parade permits for 10,000.

Fewer than 50 showed up.

"This is it?"asked one surprised mar cher, who joined the group along the way."This is it," said her companion.

The Park Police escort outnumbered the marchers.

The media, however, turned out in force, scrambling for Sunday news on a blamy, Indian summer day. Reporters and photographers dogged the marchers from the White House to the Capitol, while television crews zeroed in for close-ups.

Jeanne-Marie Weber, a free-lance interior designer from Chevy Chase who organized the march, said the poor turnout was "proof of harassment and fright" of landlord retaliation.

But she was pleased with the media turnout and gratified that D.C. Mayor Marion Barry had proclaimed yesterday National Tenants' Day.

At the Capitol, the group of marchers heard speeches from Rep. Michael D. Barnes (D-Md.), former Virginia delegate Ira Lechner, D.C. City Councilwoman Hilda H. Mason (S-At Large) and tenant organizers from New Jersey, Pennsylvania and other jurisdictions.

There were other demonstrations in the city yesterday -- both official and unofficial.

Near the entrance to the Smithsonian Institution on the Mall, about 30 disabled persons -- some in wheel chairs, some on crutches, some accompanied by guide dogs -- celebrated what was also Disabled Peoples' Civil Rights Day.

And in the parks, the streets and playing fields, thousands of other residents simply demonstrated their appreciation of the sunny day. Some went sailing on the Potomac, while others rode bikes, played ball, jogged fished, threw Fresbees, or trimmed their front lawns for what may be the last time of the year.

The demonstration for disabled people was one of 47 such rallies planned to take place simultaneously in other cities yesterday. Some 400 of the handicapped had been expected here. Only 30 showed up.

Terrance O'Rourke, president of the American Coalition of Citizens with Disabilities Inc., noted that it is diffcult for most disabled persons to manuever about.

"Some of the people who are here, I'm sure, took five hours to get here when it would have taken another person seven or eight minutes.

Yesterday was also "leaf day" in Shenandoah National Park in Virginia and many Washington area residents took to the westward-bound highways to view the autumn foliage.

Traffic flowing into the park was described as bumper to bumper for miles.

About 12,000 cars moved through the park yesterday, a park ranger said, and the lodges and camp grounds were filled.

Back in the Washington area, however, those who stayed home found other ways to enjoy the 70-degree weather. They shed the parkas and woolen clothes of the recent snowfall to shorts and T-shirts again. Some people were walking barefoot across the Mall.

"I can't stand it too hot or too cold. This is just the kind of weather I like," said Robert Jackson of Southeast Washington as he relaxed on a bench near the Tidal Basin. He'd already set up his fishing pole so that it would stand up by itself. An empty bucket for fish sat beside him waiting.

Temperatures reached 77 yesterday without a cloud in the sky for the most part, and were scheduled to hit 80 today. Weathermen credited the warm weather to a stationary high pressure system over the western part of the Atlantic which has extended inland, according Brian Smith of the National Weather Service.

There is currently a cold front over the middle of the nation, but right now "It doesn't seem inclined to come to us," Smith said.