Temperature in Degrees F.
Relative Humidity	70	75	80	85	90	95	100	105	110	115	120
0%	64	69	73	78	83	87	91	95	99	103	107
10%	65	70	75	80	85	90	95	100	105	111	116
20%	66	72	77	82	87	93	99	105	112	120	130
30%	67	73	78	84	90	96	104	113	123	135	148
40%	68	74	79	86	93	101	110	123	137	151
50%	69	75	81	88	96	107	120	135	150
60%	70	76	82	90	100	114	132	149
70%	70	77	85	93	106	124	144
80%	71	78	86	97	113	136
90%	71	79	88	102	122
100%	72	80	91	108

How To Use Heat Index:

1. Across top locate Temperature

2. Down left side locate Relative Humidity

3. Follow across and down to find Apparent Temperature *

4. Determine Heat Stress Risk on chart below

Apparent Temperature	Heat Stress Risk with Physical Activity and/or Prolonged Exposure
90° to 105°	Heat cramps or heat exhaustion possible
105° to 130°	Heat cramps or heat exhaustion likely, Heatstroke possible
130° and up	Heatstroke highly likely

* Combined index of heat and humidity. In other words, what it feels like to the body

This heat index chart is designed to provide general guidelines for assessing the potential severity of heat stress. Individual reactions to heat will vary. In addition, studies indicate that the susceptibility to heat disorders tends to increase with age. Exposure to full sunshine can increase Heat Index values by up to 15° F.

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Article Updated August 27, 2007

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