Heat Index Charts

To use the heat index charts, find the appropriate temperature at the top of the chart. There are two charts on this page. Read down until you are opposite the humidity/dewpoint. The number which appears at the intersection of the temperature and humidity/dewpoint is the heat index.

Heat Index Chart (Temperature & Dewpoint)
Dewpoint
( F)
Temperature ( F)
90919293949596979899100101102103104105
65 94 95 96 97 98100101102103104106107108109110112
66 94 95 97 98 99100101103104105106108109110111112
67 95 96 97 98100101102103105106107108110111112113
68 95 97 98 99100102103104105107108109110112113114
69 96 97 99100101103104105106108109110111113114115
70 97 98 99101102103105106107109110111112114115116
71 98 99100102103104106107108109111112113115116117
72 98100101103104105107108109111112113114116117118
73 99101102103105106108109110112113114116117118119
74100102103104106107109110111113114115117118119121
75101103104106107108110111113114115117118119121122
76102104105107108110111112114115117118119121122123
77103105106108109111112114115117118119121122124125
78105106108109111112114115117118119121122124125126
79106107109111112114115117118120121122124125127128
80107109110112114115117118120121123124126127128130
81109110112114115117118120121123124126127129130132
82110112114115117118120122123125126128129131132133
Note: Exposure to full sunshine can increase HI values by up to 15 F


Heat Index Chart (Temperature & Relative Humidity)
RH
(%)
Temperature ( F)
90919293949596979899100101102103104105
90119123128132137141146152157163168174180186193199
85115119123127132136141145150155161166172178184190
80112115119123127131135140144149154159164169175180
75109112115119122126130134138143147152156161166171
70106109112115118122125129133137141145149154158163
65103106108111114117121124127131135139143147151155
60100103105108111114116120123126129133136140144148
55 98100103105107110113115118121124127131134137141
50 96 98100102104107109112114117119122125128131135
45 94 96 98100102104106108110113115118120123126129
40 92 94 96 97 99101103105107109111113116118121123
35 91 92 94 95 97 98100102104106107109112114116118
30 89 90 92 93 95 96 98 99101102104106108110112114
Note: Exposure to full sunshine can increase HI values by up to 15 F

For the more ambitious who would like to calculate the heat index, here is the formula:

Formula for finding heat index

where:

HI = Heat Index
T = Temperature ( F)
RH = Relative Humidity (%)


Source: Meteorology for Scientists and Engineers, 2nd edition by Roland B. Stull


Better yet, input any temperature above 80 Fahrenheit along with a relative humidity.

in Fahrenheit

Enter in the air temperature ( Tair ) in degrees Fahrenheit and relative humidity ( RH ) in percent ( without the % sign ), then click on the Calculate HI to compute the heat index ( HI ).

Tair in °F RH Tdp =

in Fahrenheit

Enter in the air temperature ( Tair ) the dew point temperature ( Tdp ) in degrees Fahrenheit, then click on the Calculate HI to compute the heat index ( HI ).

Tair in °F Tdp in °F RH =



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