Because the Weather Stress Index considers temperature, relative humidity and wind speed, says climatologist Laurence Kalkstein, it could be useful in alerting public health officials when heatstroke or other severe conditions are imminent.

In a preliminary study he and his associates were given statistics on the number of people who died of heatstroke during a particularly severe 1980 heat wave in Kansas City.

"We initially determined," says Kalkstein, "that maximum temperature doesn't seem to be the thing that kills people with heatstroke." The variable most contributory to heatstroke deaths was "minimum temperature the night before, not maximum temperature."

The other two important variables, wind and humidity, were equally surprising to Kalkstein: "Wind was important, but in a way you might not think. The higher the wind, the more people that died."

Also, the lower the relative humidity, the more people died.

"We are suggesting," says Kalkstein, emphasizing the preliminary nature of the one-city study, "that these people are dying of dessication, dehydration."

Kalkstein points out that some cities have been known to pass out fans to elderly and poor people as heatstroke conditions build up. "Now," he says, "I'm picturing these people in a windy situation where it's actually killing them faster."