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)
Dewpoint (° F)	90	91	92	93	94	95	96	97	98	99	100	101	102	103	104	105
65	94	95	96	97	98	100	101	102	103	104	106	107	108	109	110	112
66	94	95	97	98	99	100	101	103	104	105	106	108	109	110	111	112
67	95	96	97	98	100	101	102	103	105	106	107	108	110	111	112	113
68	95	97	98	99	100	102	103	104	105	107	108	109	110	112	113	114
69	96	97	99	100	101	103	104	105	106	108	109	110	111	113	114	115
70	97	98	99	101	102	103	105	106	107	109	110	111	112	114	115	116
71	98	99	100	102	103	104	106	107	108	109	111	112	113	115	116	117
72	98	100	101	103	104	105	107	108	109	111	112	113	114	116	117	118
73	99	101	102	103	105	106	108	109	110	112	113	114	116	117	118	119
74	100	102	103	104	106	107	109	110	111	113	114	115	117	118	119	121
75	101	103	104	106	107	108	110	111	113	114	115	117	118	119	121	122
76	102	104	105	107	108	110	111	112	114	115	117	118	119	121	122	123
77	103	105	106	108	109	111	112	114	115	117	118	119	121	122	124	125
78	105	106	108	109	111	112	114	115	117	118	119	121	122	124	125	126
79	106	107	109	111	112	114	115	117	118	120	121	122	124	125	127	128
80	107	109	110	112	114	115	117	118	120	121	123	124	126	127	128	130
81	109	110	112	114	115	117	118	120	121	123	124	126	127	129	130	132
82	110	112	114	115	117	118	120	122	123	125	126	128	129	131	132	133
Note: Exposure to full sunshine can increase HI values by up to 15° F

Heat Index Chart (Temperature & Relative Humidity)
RH
(%) Temperature (° F)

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

90 119 123 128 132 137 141 146 152 157 163 168 174 180 186 193 199

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 99 101 102 104 106 108 110 112 114

Note: Exposure to full sunshine can increase HI values by up to 15° F

**Heat Index Chart (Temperature & 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	163	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	108	110	112	114
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 ( T_air ) in degrees Fahrenheit and relative humidity ( RH ) in percent ( without the % sign ), then click on the Calculate HI to compute the heat index ( HI ).
T_air in °F		RH				T_dp =

in Fahrenheit Enter in the air temperature ( T_air ) the dew point temperature ( T_dp ) in degrees Fahrenheit, then click on the Calculate HI to compute the heat index ( HI ).
T_air in °F		T_dp in °F				RH =

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Heat Index Charts

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[Back to main menu] [Interactive Weather Page] [Chat on IRC!]
[Announcements] [Join the mailing list!] [About me] [US Data by State] [Weather Cams] [E-mail me]