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Printable heat index chart

Heat index in degrees Fahrenheit, computed from the National Weather Service equation including both official humidity corrections. Shade, light wind. Full sun can add up to 15°F.
RH ↓ Air temp →	80°F	82°F	84°F	86°F	88°F	90°F	92°F	94°F	96°F	98°F	100°F	102°F	104°F	106°F	108°F	110°F
40%	80	81	83	85	88	91	94	97	101	105	109	114	119	124	130	136
45%	80	82	84	87	89	92	96	100	104	109	114	119	124	130	137	143
50%	81	83	85	88	91	95	99	103	108	113	118	124	131	137	144	152
55%	81	84	86	89	93	97	101	106	112	117	124	130	137	145	153	161
60%	82	84	88	91	95	100	105	110	116	123	129	137	145	153	162	171
65%	82	85	89	93	98	103	108	114	121	128	136	144	153	162	172	182
70%	83	86	90	95	100	106	112	119	126	134	143	152	161	172	182	194
75%	84	88	92	97	103	109	116	124	132	141	150	160	171	182	193	206
80%	84	89	94	100	106	113	121	129	138	148	158	169	181	193	205	219
85%	85	90	96	102	110	117	126	135	145	155	167	179	191	204	218	233
90%	86	92	98	105	113	122	131	141	152	164	176	189	202	216	231	247
95%	88	94	101	109	117	127	137	148	160	172	185	199	214	229	245	262
100%	89	96	104	112	121	132	143	155	168	181	195	210	226	243	260	278

Heat index in degrees Celsius, computed from the National Weather Service equation including both official humidity corrections. Shade, light wind. Full sun can add up to 8°C.
RH ↓ Air temp →	27°C	28°C	29°C	30°C	31°C	32°C	33°C	34°C	35°C	36°C	37°C	38°C	39°C	40°C	41°C	42°C	43°C	44°C
40%	27	28	29	30	31	32	34	35	37	39	41	43	46	48	51	54	57	60
45%	27	28	29	30	32	33	35	37	39	41	43	46	49	51	54	57	61	64
50%	27	28	30	31	33	34	36	38	41	43	46	49	52	55	58	62	65	69
55%	28	29	30	32	34	36	38	40	43	46	48	52	55	59	62	66	70	75
60%	28	29	31	33	35	37	40	42	45	48	51	55	59	63	67	71	76	81
65%	28	30	32	34	36	39	41	44	48	51	55	59	63	67	72	77	82	87
70%	29	31	33	35	38	40	43	47	50	54	58	63	67	72	77	82	88	94
75%	29	31	34	36	39	42	46	49	53	58	62	67	72	77	83	88	94	101
80%	30	32	35	38	41	44	48	52	57	61	66	71	77	83	89	95	101	108
85%	30	33	36	39	43	47	51	55	60	65	70	76	82	88	95	102	109	116
90%	31	34	37	41	45	49	54	58	64	69	75	81	88	95	102	109	117	125
95%	32	35	39	43	47	51	57	62	68	74	80	87	94	101	109	117	125	134
100%	33	36	40	44	49	54	60	66	72	78	85	92	100	108	116	125	134	143

No band — below 80°F / 27°C
Caution — fatigue possible
Extreme Caution — cramps and exhaustion possible
Danger — exhaustion likely, heat stroke possible
Extreme Danger — heat stroke highly likely

The numbers above are the answer for the values the page loaded with. Changing the controls needs JavaScript — without it the calculator cannot recalculate, so read the figures as one worked example rather than a live result.

Where can I get a printable heat index chart?

This one. Pick Fahrenheit or Celsius above and print — the page is laid out for a single sheet, drops the site furniture, and keeps the band colours and the legend. Every cell is computed from the National Weather Service equation rather than copied from an image, so the Celsius version is a real conversion rather than a redrawn approximation.

How to read it

Find the air temperature along the top, the relative humidity down the side, and read the heat index where they meet. The colour is the risk band, and the legend under the chart names each one.

Three things worth knowing before you pin it up:

It is a shade chart. In full sun, read it as though you were one or two columns hotter.
Below 80°F there is no band. The grid starts at 80°F because that is where the official regression starts applying.
The categories assume a healthy adult at rest or light activity. Anyone working, running, elderly, very young, or in protective clothing crosses each line earlier.

What to do at each band

If you are printing this for a wall, the four lines below are the part people will actually read.

NWS risk categories, paraphrased for posting. Conditions and precautions, not medical advice.
Band	Heat index	Action
Caution	80–90°F 27–32°C	Drink water regularly. Take breaks if working or exercising outdoors.
Extreme Caution	90–103°F 32–39°C	Limit strenuous activity. Rest in shade often. Drink before feeling thirsty.
Danger	103–125°F 39–52°C	Avoid strenuous activity outdoors. Stay in shade or air conditioning.
Extreme Danger	125°F and above 52°C and above	Stay indoors in air conditioning if at all possible. Cancel outdoor work.

Where this chart differs from the printed NOAA table

In twelve cells — relative humidity above 85%, air temperature between 80 and 87°F — this chart reads up to about 2°F hotter than the chart NOAA prints. That is not an error in either place. The NWS equation page specifies a correction that adds to the result in that corner, and the printed table does not apply it, while the NWS's own online calculator does.

This chart follows the equation. How the heat index is calculated sets out both corrections in full, and the chart guide explains how to read the grid in more depth.

Common questions

Is this the official NOAA chart?

It is the same equation and the same four risk categories, computed rather than reproduced. It is not an official NOAA document and is not endorsed by them. Where it differs from the printed NOAA table is the twelve cells above 85% humidity between 80 and 87°F, where the printed table omits a correction the equation applies — this chart follows the equation.

Why does the Celsius chart use different temperature steps?

Because a direct conversion of the Fahrenheit column headings would give values like 26.7°C, which are useless on a wall. The Celsius chart is computed on whole Celsius degrees from 27 to 44, so the row and column labels are numbers people actually read off a thermometer.

Can I use this at a school or a worksite?

Yes, print and post it freely. Bear in mind it is a shade chart: for sports and outdoor work, governing bodies and OSHA materials generally use WBGT, which also accounts for sun and wind. If that is what your policy references, the WBGT estimator is the better page.

How do I save it as a PDF instead of printing?

Use your browser's print dialog and choose “Save as PDF” as the destination — on macOS it is in the PDF dropdown, on Windows and Android it is a printer option. The page is styled for print, so the file will not contain the navigation or this text.

Does the chart include the effect of direct sunlight?

No. Like the official chart it is a shade value. The National Weather Service notes full sunshine can raise the effective heat index by up to 15°F, which for a chart on a sunny worksite means reading one to two columns to the right of where you actually are.

Sources

Published 30 July 2026