Heat Index Chart
% Relative Humidity

15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
T
e
m
p
e
r
a
t
u
r
e
110
108
112
117
123
130
105
102
105
108
113
117
122
130
100
97
98
102
104
107
110
115
120
126
132
95
91
93
95
96
98
100
104
106
109
113
119
124
130
90
86
87
88
90
91
92
95
97
98
100
103
106
110
114
117
121
85
81
82
83
84
85
86
87
88
89
90
92
94
96
97
100
102
80
76
77
78
78
79
79
80
81
82
83
84
85
86
87
88
89
Legend
80-89 degrees

Fatigue is possible with prolonged exposure and/or physical activity.
90-104 degrees

Sunstroke, heat cramps and heat exhaustion are possible with prolonged exposure and/or physical activity.
105-129 degrees

Sunstroke, heat cramps and heat exhaustion are likely. Heat stroke is possible with prolonged exposure and/or physical activity.
130+ degrees

Heatstroke/sunstroke is highly likely with continued exposure.


Above is a heat index (or apparent temperature) chart showing various combinations of air temperature versus relative humidity.

To use the chart, locate the air temperature along the left column and the relative humidity along the top. The cell where the two intersect is the heat index.

For example, an air temperature of 90 degrees fahrenheit and a relative humidity of 60 percent intersect at a heat index of 100 degrees. In other words, the temperature would feel like 100 degrees with this humidity/temperature combination.

Heat index values were devised for shady light wind conditions. Exposure to full sunlight can increase values by up to 15 degrees farenheit.

First aid treatment suggestions for heat-related illnesses can be obtained from local red cross offices, hospitals, clinics, public health agencies and physicians.

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