Heat Index

The human body contains several mechanisms to maintain its internal operating temperature at 37C.

When threatened with above normal temperatures, the body will try to dissipate excess heat by varying the rate and depth of blood circulation, by losing water through the skin and sweat glands, and, as a last resort, by panting.
When weather conditions force the air temperature above 32C and the relative humidity is high, the body is doing everything it can to maintain its normal temperature. Unfortunately, conditions can exceed the body's ability to cope with the combined affects of heat and humidity.
At such times the body may sucumb to any of a number of heat disorders including sun stroke, heat cramp, heat exhaustion and heat stroke.

To use the heat index chart below, find the temperature on the left of the chart. Read across until you reach the desired relative humidity. The number which appears at the intersection of the temperature and relative humidity is the heat index. Note that the heat index under direct sunlight will be 8C higher than the number shown in the chart.

Relative Humidity Temp C	50%	60%	70%	80%	90%	100%
28	28.4	29.4	30.7	32.1	33.7	35.6
29	29.7	31.0	32.7	34.7	37.1	39.7
30	31.0	32.8	35.0	37.7	40.7	44.2
31	32.6	34.8	37.6	40.9	44.7	49.0
32	34.4	37.1	40.4	44.4	49.0	54.2
33	36.3	39.5	43.5	48.1	53.5	59.7
34	38.4	42.2	46.8	52.2	58.4	65.5
35	40.7	45.1	50.3	56.5	63.7	71.7
36	43.1	48.1	54.2	61.2	69.2	78.2

Extreme Caution - Heat cramp and exhaustion possible.

Danger - Heat exhaustion likely.

Extreme Danger - Heat stroke imminent.