Heat Index (Apparent Temperature) Chart

The Heat Index (HI) is the temperature the body feels when heat and humidity are combined. The chart below shows the HI that corresponds to the actual air temperature and relative humidity. (NOTE: This chart is based upon shady, light wind conditions. Exposure to direct sunlight can increase the HI by up to 15°F.)

(Due to the nature of the heat index calculation, the values in the tables below have an error of +/- 1.3°F.) 

Relative Humidity (in percent)

Air
Temp
(in F)
  0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100  
140 125                                          
135 120 128                                        
130 117 122 131                                      
125 111 116 123 131 141                                  
120 107 111 116 123 130 139 148                              
115 103 107 111 115 120 127 135 143 151                          
110 99 102 105 108 112 117 123 130 137 143 150                      
105 95 97 100 102 105 109 113 118 123 129 135 142 149                  
100 91 93 95 97 99 101 104 107 110 115 120 126 132 138 144              
95 87 88 90 91 93 94 96 98 101 104 107 110 114 119 124 130 136          
90 83 84 85 86 87 88 90 91 93 95 96 98 100 102 106 109 113 117 122      
85 78 79 80 81 82 83 84 85 86 87 88 89 90 91 93 95 97 99 102 105 108  
80 73 74 75 76 77 77 78 79 79 80 81 81 82 83 85 86 86 87 88 89 91  
75 69 69 70 71 72 72 73 73 74 74 75 75 76 76 77 77 78 78 79 79 80  
70 64 64 65 65 66 66 67 67 68 68 69 69 70 70 70 70 71 71 71 71 72  

 

Heat Index General Effect of Heat Index on People in Higher Risk Groups
80° to 89° - Very Warm Fatigue possible with prolonged exposure and/or physical activity.
90° to 104° - Hot Sunstroke, heat cramps and heat exhaustion possible with prolonged exposure and/or physical activity.
105° to 129° - Very Hot Sunstroke, heat cramps or heat exhaustion likely, and heatstroke possible with prolonged exposure and/or physical activity.
130° or higher - Extremely Hot Heat/sunstroke highly likely with continued exposure.

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