Heat Index

Equivalent heat index temperatures at various temperatures and corresponding relative humidities

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The heat index is a measure how an average person perceives temperature and humidity and how it affect the human body to cool it self.

Apparent Temperature Heat Stress Index (^oF)
Relative Humidity %RH	Temperature (^oF)
Relative Humidity %RH	70	75	80	85	90	95	100	105	110	115	120	125	130	135	140
0	64	69	73	78	83	87¹⁾	91	95	99	103	107	111	117	120	125
5	64	69	74	79	84	88	93	97	102	107	111	115	122	128
10	65	70	75	80	85	90²⁾	95	100	105	111	116	123	131
15	65	71	76	81	85	91	97	102	106	115	123	131
20	66	72	77	82	87	93	99	105	112	120	130	141
25	66	72	77	83	88	94	101	109	117	127	139
30	67	73	78	84	90	96	104	113	123	135	148
35	67	73	79	85	91	98	107	118	130	143
40	68	74	79	86	93	101	110	123	137	151
45	68	74	80	87	95	104	115	129	143
50	69	75	81	88	96	107³⁾	120	135	150
55	69	75	81	89	96	110	126	142
60	70	76	82	90	100	114	132	149
65	70	76	83	91	102	119	138
70	70	77	85	93	106	124	144
75	70	77	86	95	109	130⁴⁾
80	71	77	86	97	113	136
85	71	78	87	99	117
90	71	79	88	102	122
95	71	79	89	105
100	72	80	91	106

T(^oC) = 5/9[T(^oF) - 32]

Sunstroke and heat exhaustion:

¹⁾ Caution - Fatigue is possible with prolonged exposure and/or physical activity

²⁾ Extreme Caution - Sunstroke, heat cramps and heat exhaustion are possible with prolonged exposure and/or physical activity

³⁾ Danger - Sunstroke, heat cramps and heat exhaustion are likely. Heat stroke is possible with prolonged exposure and/or physical activity

⁴⁾ Extreme Danger - Heatstroke/sunstroke is highly likely with continued exposure

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