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heat index

(National Weather Service)

What is the Heat Index?

Many residents of the northeast realize that warm, dry air seems more comfortable than warm, very moist air (unless it is too dry). An extremely humid, warm day makes one think the temperature is higher than it really is, while an extremely hot, dry day may seem to be cooler than the thermometer indicates.

One approach to describing the combined effects of temperature and humidity is the heat index. To alert the public to the dangers of exposure to extended periods of heat and the added effects of humidity, the NationalWeather Service has developed a "Heat Index" table.

To determine the heat index, find the temperature across the top of the table and the relative humidity down the left-hand side. Where the two intersect is the heat index.

Heat Index Chart (Temperature and Relative Humidity)

RH
Temperature (F)

(%) 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105

90 119 123 128 132 137 141 146 152 157 167 168 174 180 186 193 199

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 99 101 102 104 106 018 110 112 114

**Exposure to full sunshine will increase these values by up to 15慚