MID-ATLANTIC WEATHER STATION

Wind Chill + Heat Index Tables


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Wind Chill Temperatures

The Wind Chill temperatures is a measure of the relative discomfort due to the combined cold and wind. The National Weather Service uses a new wind chill formula as of November 2001, replacing an equation developed in 1945 during expirements in Antarctica. The old formula was based on how a can of water cooled in the wind.

The new formula relies on modern heat transfer theory and is based on experiments conducted in a chilled wind tunnel in Toronto, Canada. The faces of several men and women were exposed to different wind and temperature conditions to calculate the new formula.

The new formula requires stronger winds or colder temperatures to reach the wind chill levels we've talked about over the years. It appears the old formula overestimated how cold the wind makes it feel. Researchers found that wind chill temperatures of 19 below and colder on the new wind chill chart caused frostbite in 15 minutes or less.

Remember, wind chill is the temperature skin cools to due to evaporative cooling of moisture caused by the wind. Because of evaporation of perspiration, skin can actually cool to temperatures colder than the air temperature. Since cars don't perspire, they can't be cooled below the air temperature by the wind so wind chill does not apply to them.

Heat Index (Apparent Temperature)

The "heat index" or apparent temperature is a measure of discomfort due to the combination of heat and high humidity. It was developed in 1979 and is based on studies of evaporative skin cooling.
70
degF
75
degF
80
degF
85
degF
90
degF
95
degF
100
degF
105
degF
110
degF
115
degF
120
degF
125
degF
130
degF
135
degF
Relative
Humidity
0 64 69 73 78 83 87 91 95 99 103 107 111 117 120
5 64 69 74 79 84 88 93 97 102 107 111 116 122 126
10 65 70 75 80 85 90 95 100 105 111 116 123 131
15 65 71 76 81 86 91 97 102 108 115 123 131
20 66 72 77 82 87 93 99 105 112 120 130 141
25 66 72 77 83 88 94 101 109 117 127 139
30 67 73 78 84 90 96 104 113 123 135 148
35 67 73 79 85 91 98 107 118 130 143
40 68 74 79 86 93 101 110 123 137 151
45 68 74 80 87 95 104 115 129 143
50 69 75 81 88 96 107 120 135 150
55 69 75 81 89 98 110 126 142
60 70 76 82 90 100 114 132 149
65 70 76 83 91 102 119 138
70 70 77 84 93 106 124 144
75 70 77 85 95 109 130 150
80 71 78 86 97 113 136
85 71 78 67 99 117 140
90 71 79 88 102 122 150
95 71 79 89 105 126
100 72 80 90 108 131

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