Heat Index Chart Air Temperature (Degrees F) 70 75 80 85 90 95 100 105 110 115 120 Relative Humidity Apparent Temperature 0% 64 69 73 78 83 87 91 95 99 103 107 10% 65 70 75 80 85 90 95 100 105 111 116 20% 66 72 77 82 87 93 99 105 112 120 130 30% 67 73 78 84 90 96 104 113 123 135 148 40% 68 74 79 86 93 101 110 123 137 151   50% 69 75 81 88 96 107 120 135 150     60% 70 76 82 90 100 114 132 149       70% 70 77 85 93 106 124 144         80% 71 78 86 97 113 136 157         90% 71 79 88 102 122 150 170         100% 72 80 91 108 133 166           The Heat Index shows the effects of the combination of heat and humidity. The apparent tempertaure is the heat your body thinks it is. To use the chart locate the temperature along the top row and the humidity along the left hand column. Where the two intersect is the current heat index. It's usually hotter than you think!