TOPFIT Heat Index Chart

Heat Index Chart

How To Use The Heat Index Chart:

Across the top of the chart, locate the ENVIRONMENTAL TEMPERATURE i.e., the air temperature.

Down the left side of the chart, locate the RELATIVE HUMIDTY.

Follow across and down to find the APPARENT TEMPERATURE Apparent Temperature is the combined index of heat and humidity. It is an index of the body’s sensation of heat caused by the temperature and humidity (the reverse of the "wind chill factor").

Note: Exposure to full sunshine can increase Heat Index values by up to 15^oF

Environmental Temperature (^oF)
	70^o	75^o	80^o	85^o	90^o	95^o	100^o	105^o	110^o	115^o	120^o
Relative Humidity	Apparent Temperature*
0%	64^o	69^o	73^o	78^o	83^o	87^o	91^o	95^o	99^o	103^o	107^o
10%	65^o	70^o	75^o	80^o	85^o	90^o	95^o	100^o	105^o	111^o	116^o
20%	66^o	72^o	77^o	82^o	87^o	93^o	99^o	105^o	112^o	120^o	130
30%	67^o	73^o	78^o	84^o	90^o	96^o	104^o	113^o	123^o	135
40%	68^o	74^o	79^o	86^o	93^o	101^o	110^o	123^o	137	151
50%	69^o	75^o	81^o	88^o	96^o	107^o	120^o	135	150
60%	70^o	76^o	82^o	90^o	100^o	114^o	132	149
70%	70^o	77^o	85^o	93^o	106^o	124^o	144
80%	71^o	78^o	86^o	97^o	113^o	136
90%	71^o	79^o	88^o	102^o	122^o
100%	72^o	80^o	91^o	108^o
*Combined index of heat and humidity…what it "feels like" to the body. Source: National Oceanic and Atmospheric Administration

Apparent Temperature	Heat Stress Risk With Physical Activity and/or Prolonged Exposure
90 ^o - 105 ^o	Heat cramps or heat exhaustion possible
105 ^o - 130 ^o	Heat cramps or heat exhaustion likely, Heatstroke possible
130 ^oand up	Heatstroke highly likely
Note: This Heat Index chart is designed to provide general guidelines for assessing the potential severity of heat stress. Individual reactions to heat will vary. It should be remembered that heat illness can occur at lower temperatures than indicated on the chart. In addition, studies indicate that susceptibility to heat disorders tends to increase with age.