|
NWS Elko: Wind Chill Index
What is Heat Index?
[this data partially created by the American
Meteorological Society Datastreme project]
Heat kills by taxing the human body beyond its abilities. In
a normal year, about 175 Americans succumb to the demands of summer heat. Human
bodies dissipate heat by varying the rate and depth of blood circulation, by
losing water through the skin and sweat glands, and as a last resort, by panting,
when blood is heated above 98.6°F. Sweating, by itself, does nothing to cool
the body, unless the water is removed by evaporation. High relative humidity
retards evaporation.
Heat disorders generally have to do with a reduction or collapse
of the body's ability to shed heat by circulatory changes and sweating. When
heat gain exceeds the level the body can remove, the temperature of the body's
inner core begins to rise and heat related illnesses may develop.
As a result, the "Heat Index" (HI) has been developed. The HI
is the temperature the body feels when heat and humidity are combined. The table
below correlates the actual temperature and relative humidity, producing a HI.
(This chart is based upon shady, light wind conditions. Exposure to full sunshine
can increase the HI by up to 15°F.)
Heat Index, based on Temperature and DewPoint
| Air Temp |
Dew Point
(°F) |
| 50°F |
55 °F |
60 °F |
65 °F |
70 °F |
75 °F |
80 °F |
85 °F |
| 65 °F |
62.7 |
63.8 |
65.0 |
66.6 |
|
|
|
|
| 70 °F |
67.8 |
68.7 |
69.8 |
71.1 |
72.6 |
|
|
|
| 75 °F |
73.1 |
73.9 |
74.8 |
75.9 |
79.2 |
80.7 |
|
|
| 80 °F |
79.8 |
80.6 |
81.6 |
82.8 |
84.4 |
86.9 |
90.9 |
|
| 85 °F |
83.5 |
84.7 |
86.1 |
88.0 |
90.5 |
94.0 |
99.0 |
106.6 |
| 90 °F |
87.9 |
89.4 |
91.2 |
93.6 |
96.9 |
101.2 |
107.2 |
115.6 |
| 95 °F |
92.9 |
94.5 |
96.7 |
99.6 |
103.4 |
108.4 |
115.2 |
124.3 |
| 100 °F |
98.1 |
99.9 |
102.4 |
105.6 |
109.8 |
115.3 |
122.7 |
132.3 |
| 105 °F |
103.4 |
105.4 |
108.1 |
111.6 |
116.1 |
122.0 |
129.7 |
139.7 |
| 110 °F |
108.7 |
110.9 |
113.8 |
117.5 |
122.3 |
128.4 |
136.3 |
146.5 |
Heat Index, based on Temperature and Relative Humidity
| Air Temp |
Relative
Humidity (%) |
| 10% |
20% |
30% |
40% |
50% |
60% |
70% |
80% |
90% |
| 65 °F |
58.1
|
59.1
|
60.0
|
60.9
|
61.9
|
62.8
|
63.8
|
64.7
|
65.6
|
| 70 °F |
64.1
|
65.1
|
66.0
|
66.9
|
67.9
|
68.8
|
69.8
|
70.7
|
71.6
|
| 75 °F |
70.1
|
71.1
|
72.0
|
72.9
|
73.9
|
74.8
|
75.8
|
76.7
|
79.7
|
| 80 °F |
76.1
|
77.4
|
79.0
|
80.4
|
81.6
|
82.8
|
84.2
|
85.9
|
88.2
|
| 85 °F |
79.6
|
81.6
|
83.5
|
85.5
|
87.7
|
90.3
|
93.3
|
97.0
|
101.4
|
| 90 °F |
84.2
|
86.5
|
89.2
|
92.3
|
96.1
|
100.5
|
105.8
|
112.0
|
119.3
|
| 95 °F |
89.2
|
92.2
|
96.1
|
100.9
|
106.7
|
113.6
|
121.7
|
131.1
|
141.8
|
| 100 °F |
94.4
|
98.7
|
104.2
|
111.2
|
119.6
|
129.5
|
140.9
|
154.0
|
168.7
|
| 105 °F |
100.0
|
105.8
|
113.6
|
123.2
|
134.7
|
148.1
|
163.4
|
180.7
|
200.0
|
| 110 °F |
105.8
|
113.7
|
124.1
|
136.8
|
151.9
|
169.4
|
189.1
|
211.2
|
235.6
|
| 115 °F |
111.9
|
122.3
|
135.8
|
152.1
|
171.3
|
193.3
|
218.0
|
245.4
|
275.3
|
| 120 °F |
118.2
|
131.6
|
148.7
|
169.1
|
192.9
|
219.9
|
250.0
|
283.1
|
319.1
|
Any value less than 80 is considered comfortable.
Any value greater than 90 is considered extreme.
Any value greater than 100 is considered hazardous.
Any value greater than 110 is considered dangerous.
| HEAT INDEX |
POSSIBLE HEAT DISORDER |
| 80°F to 90°F |
Fatigue possible with prolonged exposure and physical activity. |
| 90°F to 105°F |
Sunstroke, heat cramps and heat exhaustion possible. |
| 105°F to 130°F |
Sunstroke, heat cramps, and heat exhaustion likely, and
heatstroke possible. |
| 130°F or more |
Heat stroke highly likely with continued exposure. |
|
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