Heat Index Chart - Relative Humidity vs. Air Temperature
As one who is severely discomforted by a combination of heat and humidity, this kind of table is of great interest. If I am going to be miserable, I want to know exactly how miserable I really am! This information is derived from NOAA Click here for a windchill chart.

Extreme Danger - Heat stroke or sun stroke likely
Danger - Sunstroke, muscle cramps and/or heat exhaustion likely
Extreme Caution - Sunstroke, muscle cramps and/or heat exhaustion possible
Caution - Fatigue possible

NOAA provides the following equation for calculating heat index:

       HI = -42.379 + 2.04901523T + 10.14333127R - 0.22475541TR - 6.83783x10-3T2

               - 5.481717x10-2R2 + 1.22874x10-3T2R + 8.5282x10-4TR2 - 1.99x10-6T2R2,

           where T = ambient dry bulb temperature (°F) R = relative humidity (integer percentage)

      "Because this equation is obtained by multiple regression analysis, (HI) has an error of ±1.3°F"

 

Air

Temp

(°F)

 Relative Humidity (%)
  40 45 50 55 60 65 70 75 80 85 90 95 100
110 136                        
108 130 137                      
106 124 130 137                    
104 119 124 131 137                  
102 114 119 124 130 137                
100 109 114 118 124 129 136              
98 105 109 113 117 123 128 134            
96 101 104 108 112 116 121 126 132          
94 97 100 102 106 110 114 119 124 129 136      
92 94 96 99 101 105 108 112 116 121 126 131    
90 91 93 95 97 100 103 106 109 113 117 122 127 132
88 88 89 91 93 95 98 100 103 106 110 113 117 121
86 85 87 88 89 91 93 95 97 100 102 105 108 112
84 83 84 85 86 88 89 90 92 94 96 98 100 103
82 81 82 83 84 84 85 86 88 89 90 91 93 95
80 80 80 81 81 82 82 83 84 84 85 86 86 87