Heat Index Chart

The NWS has devised the "HEAT INDEX" (HI), sometimes called the "apparent temperature." The HI is the temperature the body feels when the heat and humidity are combined. The table below is the Heat Index Chart. (Note: This chart is based upon shady, light wind conditions. Exposure to full sunshine can increase HI values by up to 15° F.)

	Air Temperature (Degrees F)
	70	75	80	85	90	95	100	105	110	115	120
Relative Humidity	Heat Index
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	157
90%	71	79	88	102	122	150	170
100%	72	80	91	108	133	166

Heat Index Readings and Potential Heat Related Disorders:
85 to 94 degrees F - Caution: physical activity may cause fatigue
95 to 105 degrees F - Extreme Caution: possible heat cramps and/or heat exhaustion with prolonged exposure
Above 105 degrees F - Danger: possible heat stroke with prolonged exposure; heat exhaustion and heat cramps likely