As expected, the Fourth of July weekend will be hot. And high summer temperatures can pose serious risks to health, warns a Utah Department of Health executive.

Dr. David J. Thurman, coordinator of the Epidemiological Studies Program, said that during an average summer, heat is listed as a cause of death in 200 cases. In 1980, a summer plagued with severe heat waves, there were 1,700 heat-related deaths nationally."These figures are probably the tip of the iceberg," he said. "It would appear that heat contributes directly to deaths from other causes - such as cardiovascular disease, including heart attacks and stroke."

Thurman said increased mortality from the heat is the greatest in Eastern and Midwestern cities.

The problem isn't as severe in Utah, where the humidity is lower. But with temperatures reaching 100 degrees and higher (his June was the hottest on record), the health specialist is advising Utahns to take certain common-sense preventive measures.

"Most people can and should avoid being in conditions of extreme heat for prolonged periods," he said. "We should pay particular attention to people who are at high risk, especially the elderly in nursing homes. Those homes should be air conditioned because their (lderly people's) means of regulating body temperature may not be as effective as a younger person's."

Thurman said other groups at high risk are:

-People taking certain medications, such as phenothiazine tranquilizers (hich interfere with temperature regulation), and certain drugs with anti-cholinergic properties (hich interfere with the body's ability to sweat). Hay fever pills commonly are in the latter category.

"I am not saying people shouldn't take these drugs, but they should exhibit some extra caution during a heat wave," he said.

-Children under age 4, especially when the child has diarrhea, which can contribute to dehydration; heavy alcohol drinkers; and people with chronic illnesses such as multiple sclerosis.

-People who are performing prolonged heavy physical exertion in conditions of extreme heat, especially people who are not adapted to those conditions.

Thurman said air conditioning is helpful in remedying heat-related problems. But it's expensive. Swamp coolers are a cheaper alternative, and electric fans also help up to a point by keeping the air moving. But when the temperature of the air gets in the high 90s, fans lose their effectiveness.

To weather hot temperatures, Thurman recommends that people drink extra fluids, wear light clothing and avoid prolonged exposure to the sun. People who have a daily exercise program should work out during the cooler times of day. Salt supplements are not recommended for the general public.

Thurman has some additional advice: If you feel the heat, be alert for symptoms that could indicate medical problems. They include:

-Heat cramps or even heat syncope (fainting) - a warning sign that you are stressing yourself too much in the heat.

-Heat exhaustion, which causes symptoms of dizziness, fatigue and weakness. It may or may not cause a mild elevation of body temperature of up to 102 degrees. People with such symptoms should see a physician.

-Heat stroke, a syndrome that can develop after one or two days under conditions of extreme heat stress. The body temperature may rise to 105 degrees or more. Heat stroke can cause coma or shock.It often causes death.