The D.C. Medical Examiner's office has ruled the deaths of two Washington women last month were the result of hyperthermia, or an abnormally high body temperature, caused by the hot weather.

The two deaths are the first in the District directly related to heat this year, according to Dr. Stuart Dawson, deputy medical examiner.

Mannie Dixon, 57, of 501 Virginia Ave. SE, died July 18 after several hours outside in the heat, according to officials. Police said the woman could not find her apartment key and waited several hours for a relative before notifying the resident manager, who admitted her to the apartment.

When her relatives came home, the woman was in a semi-conscious condition. Dixon's temperature had reached 107 degrees by the time she was taken to Capitol Hill Hospital, where she died several hours later, officials said.

The next day, Minnie Mitchell, 84, a resident of the city-run Regency House, 5201 Connecticut Ave., was found semi-conscious in an elevator there, according to police. Her temperature was recorded at 106 degrees at George Washington University Hospital, where she died, officials said.

"This is the first time I have heard about it," James E. Clay, the city's housing director said yesterday.

Although the police report stated that air conditioning in the building had been off for five weeks, Clay said the air conditioning was off for 10 days while a new system was being installed. He said installation was completed July 23.

High temperatures for the two days on which the women died were 96 degrees and 92 degrees, and the air quality index for July 19 was 135, or unhealthful.

Yesterday's high was 93 degrees, and highs from 90 to the low 90s are expected for the next several days, according to the National Weather Service.

Richard Kenney, chairman of the physiology department at George Washington University's medical school, said the continuing hot weather creates conditions that could lead to hyperthermia, especially in the elderly.

"The dangers of high temperature increase as the heat wave goes on. Incidents become more common because people become a little bit dehydrated day by day," Kenney cautioned. Therefore, he said, after several days of high temperatures the stress necessary to cause failure of the body's cooling mechanisms "is quite small."

People who live in the city are more prone to suffering from the heat than others because of the high amount of heat radiated by pavement and buildings, Kenney said.

"The body is pretty good at cooling itself if it has enough fluids," he said. But he noted the amount needed is more than people usually think. "Outside on a day like this, moving about quietly, a person can require more than a quart of fluid an hour.

"My rule of thumb is keep drinking to satisfy your thirst and then drink half as much again," Kenney said.

To help the body keep cool, Kenney gave these tips:

* Encourage air movement in the space where you are. If inside, make certain there is adequate ventilation. It may be better to go outside if there is a breeze.

* Adjust clothing to get good air movement. This includes wearing loose, cotton clothing, wearing shirts outside rather than tucked in and keeping collars loose.

* Avoid oversalting and avoid alcohol. Salt tablets can be counterproductive and generally should be avoided.

Alcohol makes the body excrete more fluids through the kidneys, thereby depriving the body of the ability to lose those fluids through sweat.