Heat Index Charts


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 table below may be used to estmate the heat index. For example, with a dew point of 79oF and RH of 70% the heat index is 106oF. The heat index (HI) is an accurate measure of how hot it feels when the affects of humidity are added to high temperature.

When the heat index is between 90oF and 104oF sunstroke, heat cramps or heat exhaustion are possible with prolonged exposure and physical activity. When the index is between 105oF and 129oF sunstroke, heat cramps, or heat exhaustion is likely and heatstroke is possible. Heat indices of 130o 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. For more information on the Heat Index and heatwave safety tips see the National Weather Service Internet Weather Source Page.

Heat Index Chart (Temperature and Dewpoint)
Dewpoint
(oF)		 Temperature (oF)
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 15oF

Heat Index Chart (Temperature & Relative Humidity)
RH
(%)		 Temperature (oF)
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 15oF