Heat load in various parts of Israel

Maintenance of normal body temperature in man is achieved by sweat evaporation which depends on atmospheric cooling (evaporating) power. The correct physiological expression of the external heat load, at a given time or place, requires consideration of all climatic factors directly influencing atmospheric evaporating power. The discomfort index (DI) was found to be easy to measure or compute and of physiological significance. The DI was computed for each summer month in 28 towns in Israel, to determine the number of hours per day in which heat load was medium (DI 24.1-28.0) or heavy (DI 28). It was also determined how many hours per day in each summer month the climate was mild or cool (air temperature below 22°C). The findings confirm the presence of four distinct climatic areas in Israel: The Syrian-African rift (from Tiberias to Ophira) is the hottest and the only area in Israel in which there is a heavy heat load for several hours per day. The second hottest area is the Mediterranean seashore between Naharia and El Arish and the third is the northern Negev. The coolest area is the mountain area from the Galilee to the Negev. Elevation above sea level is of great importance, as was learned from comparing settlements located close to each other, but at different elevations. It is suggested that weather forecasts would be more meaningful for the population if presented as the number of hours per day with medium or heavy heat loads.