It was in the mid-80s by early yesterday afternoon, but a pleasant breeze fanned the fully occupied benches in front of The Roosevelt for Senior Citizens apartment building on 16th Street NW.

One 74-year-old man said he sat outside to gain relief from his hot apartment. "That air conditioning hasn't worked in three weeks," said the man, who declined to give his name. "I have to come out."

"I try to stay out of the heat, stay out of the sun," said another bench-sitter, Mary Smith, 79, whose air conditioning is working but who went outside for the company. "Try to make the best of it."

Few residents of the Roosevelt ventured for long onto the hot Washington streets yesterday, a day when the temperature crawled up to 91. Experts say the elderly are particularly vulnerable to summer heat, as are the very young and those on certain medications such as diuretics, antipsychotic drugs or drugs for high blood pressure.

"Especially early in the hot season, when people have not fully acclimatized and are not used to being in the sun, they don't sweat efficiently and don't cool efficiently," said Dr. Tom Clark of the Capitol Hill Hospital emergency room.

That leads to heat cramps, heat exhaustion and other problems, he said. Clark said he is surprised he has seen few such problems yet, but "July and August are coming, so I'm sure we'll see plenty."

Not only does normal aging diminish the body's ability to sweat, which dissipates heat, but the elderly are more likely to be on prescription drugs, or have heart or lung diseases, which also impair functioning, medical experts say.

They advise the elderly to move around as little as possible, stay near an air conditioner, wear hats outside, eat light meals and wear cool clothing.

People with elderly relatives should stop by more frequently to check on them during hot weather, Clark said.

Virginia Power and Virginia's Department for the Aging have begun a program under which trained meter readers will keep an eye on elderly residents who sign up for a new "Gatekeeper" program. The utility, which serves 80 percent of the state's population, began sending out information on the program with the batch of bills it mailed yesterday.

The program trains meter readers to watch for signs of distress or neglect, such as piled-up mail or an unkempt yard, and report such information to local social service agencies.

It is modeled after a program begun three years ago in Puget Sound, Wash., that already has saved lives there, said utility spokesman Carl F. Baab.

The program is open to those who consider themselves elderly, and is the only program of its kind in the Washington area, Baab said.

The District's recreation and senior centers, a traditional refuge from the heat for many, were closed yesterday. But not all the area's elderly were uncomfortable.

In the cool tree-shaded precincts of Rock Creek Park, Eveline Krogel, a resident of the Army Distaff Foundation home, described how she staves off the heat: "I take showers and I fan myself. In the evening, we sit out on the patio."

Many of the home's 294 residents -- all women over 62 who served in the armed forces or are related to a service member -- were away for the holiday.

Those who stayed could enjoy the air-conditioned library or lounges. Krogel escorted a visitor to the back patio and pointed to one of her remedies for the heat: a tree swing.

"That's where I go to get the breeze," she said.