Heat Index Charts
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The heat index (sometmes called the apparent temperature) is a measure of the contribution that high temperature and high humidity (expressed either as relative humidity (RH) or dew point temperature) make in reducing the body's ability to cool itself. The Heat Index calculator or tables below may be used to estmate the heat index. For example, with a temperature of 90° F and RH of 70% the heat index is 106° F or 41° C. The heat index (HI) is an accurate measure of how hot it really feels when the affects of humidity are added to high temperature.
When the heat index is between 90° F and 104° F sunstroke, heat cramps or heat exhaustion are possible with prolonged exposure and physical activity. When the index is between 105° F and 129° F sunstroke, heat cramps, or heat exhaustion is likely and heatstroke is possible. Heat indices of 130° or higher will result in heatstroke or sunstroke quickly.
To reduce the risk of the danger from high humidity and high temperature wear light and loose fitting clothing and a large hat. Stay in the shade as much as possible, avoid alcoholic beverages, and drink water frequently. It is usually best to perform strenuous outdoor activity early in the morning or during the evening hours when the heat index is expected to be relatively low.
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Heat Index Chart (Temperature & Dewpoint)
Dewpoint
(° F)
|
Temperature (° F)
|
| 90
|
91
|
92
|
93
|
94
|
95
|
96
|
97
|
98
|
99
|
100
|
101
|
102
|
103
|
104
|
105
|
| 65
|
94
|
95
|
96
|
97
|
98
|
100
|
101
|
102
|
103
|
104
|
106
|
107
|
108
|
109
|
110
|
112
|
| 66
|
94
|
95
|
97
|
98
|
99
|
100
|
101
|
103
|
104
|
105
|
106
|
108
|
109
|
110
|
111
|
112
|
| 67
|
95
|
96
|
97
|
98
|
100
|
101
|
102
|
103
|
105
|
106
|
107
|
108
|
110
|
111
|
112
|
113
|
| 68
|
95
|
97
|
98
|
99
|
100
|
102
|
103
|
104
|
105
|
107
|
108
|
109
|
110
|
112
|
113
|
114
|
| 69
|
96
|
97
|
99
|
100
|
101
|
103
|
104
|
105
|
106
|
108
|
109
|
110
|
111
|
113
|
114
|
115
|
| 70
|
97
|
98
|
99
|
101
|
102
|
103
|
105
|
106
|
107
|
109
|
110
|
111
|
112
|
114
|
115
|
116
|
| 71
|
98
|
99
|
100
|
102
|
103
|
104
|
106
|
107
|
108
|
109
|
111
|
112
|
113
|
115
|
116
|
117
|
| 72
|
98
|
100
|
101
|
103
|
104
|
105
|
107
|
108
|
109
|
111
|
112
|
113
|
114
|
116
|
117
|
118
|
| 73
|
99
|
101
|
102
|
103
|
105
|
106
|
108
|
109
|
110
|
112
|
113
|
114
|
116
|
117
|
118
|
119
|
| 74
|
100
|
102
|
103
|
104
|
106
|
107
|
109
|
110
|
111
|
113
|
114
|
115
|
117
|
118
|
119
|
121
|
| 75
|
101
|
103
|
104
|
106
|
107
|
108
|
110
|
111
|
113
|
114
|
115
|
117
|
118
|
119
|
121
|
122
|
| 76
|
102
|
104
|
105
|
107
|
108
|
110
|
111
|
112
|
114
|
115
|
117
|
118
|
119
|
121
|
122
|
123
|
| 77
|
103
|
105
|
106
|
108
|
109
|
111
|
112
|
114
|
115
|
117
|
118
|
119
|
121
|
122
|
124
|
125
|
| 78
|
105
|
106
|
108
|
109
|
111
|
112
|
114
|
115
|
117
|
118
|
119
|
121
|
122
|
124
|
125
|
126
|
| 79
|
106
|
107
|
109
|
111
|
112
|
114
|
115
|
117
|
118
|
120
|
121
|
122
|
124
|
125
|
127
|
128
|
| 80
|
107
|
109
|
110
|
112
|
114
|
115
|
117
|
118
|
120
|
121
|
123
|
124
|
126
|
127
|
128
|
130
|
| 81
|
109
|
110
|
112
|
114
|
115
|
117
|
118
|
120
|
121
|
123
|
124
|
126
|
127
|
129
|
130
|
132
|
| 82
|
110
|
112
|
114
|
115
|
117
|
118
|
120
|
122
|
123
|
125
|
126
|
128
|
129
|
131
|
132
|
133
|
| Note: Exposure to full sunshine can increase HI values by up to 15° F
|
Heat Index Chart (Temperature & Relative Humidity)
RH
(%)
|
Temperature (° F)
|
| 90
|
91
|
92
|
93
|
94
|
95
|
96
|
97
|
98
|
99
|
100
|
101
|
102
|
103
|
104
|
105
|
| 90
|
119
|
123
|
128
|
132
|
137
|
141
|
146
|
152
|
157
|
163
|
168
|
174
|
180
|
186
|
193
|
199
|
| 85
|
115
|
119
|
123
|
127
|
132
|
136
|
141
|
145
|
150
|
155
|
161
|
166
|
172
|
178
|
184
|
190
|
| 80
|
112
|
115
|
119
|
123
|
127
|
131
|
135
|
140
|
144
|
149
|
154
|
159
|
164
|
169
|
175
|
180
|
| 75
|
109
|
112
|
115
|
119
|
122
|
126
|
130
|
134
|
138
|
143
|
147
|
152
|
156
|
161
|
166
|
171
|
| 70
|
106
|
109
|
112
|
115
|
118
|
122
|
125
|
129
|
133
|
137
|
141
|
145
|
149
|
154
|
158
|
163
|
| 65
|
103
|
106
|
108
|
111
|
114
|
117
|
121
|
124
|
127
|
131
|
135
|
139
|
143
|
147
|
151
|
155
|
| 60
|
100
|
103
|
105
|
108
|
111
|
114
|
116
|
120
|
123
|
126
|
129
|
133
|
136
|
140
|
144
|
148
|
| 55
|
98
|
100
|
103
|
105
|
107
|
110
|
113
|
115
|
118
|
121
|
124
|
127
|
131
|
134
|
137
|
141
|
| 50
|
96
|
98
|
100
|
102
|
104
|
107
|
109
|
112
|
114
|
117
|
119
|
122
|
125
|
128
|
131
|
135
|
| 45
|
94
|
96
|
98
|
100
|
102
|
104
|
106
|
108
|
110
|
113
|
115
|
118
|
120
|
123
|
126
|
129
|
| 40
|
92
|
94
|
96
|
97
|
99
|
101
|
103
|
105
|
107
|
109
|
111
|
113
|
116
|
118
|
121
|
123
|
| 35
|
91
|
92
|
94
|
95
|
97
|
98
|
100
|
102
|
104
|
106
|
107
|
109
|
112
|
114
|
116
|
118
|
| 30
|
89
|
90
|
92
|
93
|
95
|
96
|
98
|
99
|
101
|
102
|
104
|
106
|
108
|
110
|
112
|
114
|
| Note: Exposure to full sunshine can increase HI values by up to 15° F
|
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