Humidex

Humidex is a temperature and humidity index used by Canadian meteorologists to evaluate a person’s subjective feeling in hot weather.

Content

General data

Humidex is a dimensionless quantity based on the dew point . This index is widely used in Canadian weather reports in the summer.

According to the Canadian Meteorological Service, Humidex values above 30 cause some discomfort, above 40 - great discomfort, and values above 45 are dangerous. If humidex reaches 54, heat stroke is inevitable. Wind influence does not take this index into account.

The formula for determining the index was developed by JM Masterton and FA Richardson in 1979. Humidex is different from the heat index used in the United States , which is more based on the dew point , rather than relative humidity .

Records

The record index value was recorded on July 25, 2007, when in the Canadian city of Carman it soared to 53.0 ^[1] . He broke the previous record of 52.1, established in 1953 in the city of Windsor (Ontario) (although the residents of Windsor would not have known about it at that time, since the index was not yet invented).

Formula

Suppose the temperature is 30 ° C and the dew point is 15 ° C, then the index value will be 34 (note that humidex is a dimensionless value, but this number shows the approximate temperature in degrees Celsius ). If the temperature stays at 30 ° C and the dew point rises to 25 ° C, the index value rises to 42. Humidex is usually higher than the heat index used in the United States at the same temperature and relative humidity.

Humidex is calculated by the following formula:

Humidex = (air temperature in degrees Celsius) + h

h = 0.5555 × ( e - 10.0)

e = 6.11 × exp [5417.7530 × ((1 / 273.16) - (1 / dew point in Kelvin ))]

The complete formula looks like this:

{\text{Humidex}}={\text{Air temperature}}\ +\ 0.5555\times (6.11\times e^{5417.7530\times \left({\frac {1}{273.16}}-{\frac {1}{\text{dewpoint in kelvins}}}\right)}-10)

{\ displaystyle {\ text {Humidex}} = {\ text {Air temperature}} \ + \ 0.5555 \ times (6.11 \ times e ^ {5417.7530 \ times \ left ({\ frac {1} {273.16}} - { \ frac {1} {\ text {dewpoint in kelvins}}} \ right)} - ​​10)}

Humidex dew point calculations

		Temperature, ° C
		15	sixteen	17	18	nineteen	20	21	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43
Point dew, ° C
	ten	sixteen	17	18	nineteen	20	21	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44
	eleven	17	18	nineteen	20	21	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45
	12	17	18	nineteen	20	21	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45
	13	18	nineteen	20	21	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46
	14	18	nineteen	20	21	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46
	15	nineteen	20	21	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47
	sixteen	-	21	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
	17	-	-	22	23	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
	18	-	-	-	24	25	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49
	nineteen	-	-	-	-	26	27	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49	50
	20	-	-	-	-	-	28	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49	50	51
	21	-	-	-	-	-	-	29	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49	50	51
	22	-	-	-	-	-	-	-	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49	50	51	52
	23	-	-	-	-	-	-	-	-	33	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49	50	51	52	53
	24	-	-	-	-	-	-	-	-	-	35	36	37	38	39	40	41	42	43	44	45	46	47	48	49	50	51	52	53	54
	25	-	-	-	-	-	-	-	-	-	-	37	38	39	40	41	42	43	44	45	46	47	48	49	50	51	52	53	54	55
	26	-	-	-	-	-	-	-	-	-	-	-	39	40	41	42	43	44	45	46	47	48	49	50	51	52	53	54	55	56
	27	-	-	-	-	-	-	-	-	-	-	-	-	42	43	44	45	46	47	48	49	50	51	52	53	54	55	56	57	58
	28	-	-	-	-	-	-	-	-	-	-	-	-	-	44	45	46	47	48	49	50	51	52	53	54	55	56	57	58	59

Dew Point Auxiliary Table

Temperature air, ° C	Relative humidity
Temperature air, ° C	thirty%	35%	40%	45%	50%	55%	60%	65%	70%	75%	80%	85%	90%	95%
- ten	- 23.2	- 21.8	- 20.4	- 19.1	- 17.8	- 16.8	- 15.8	- 14.9	- 14.1	- 13.35	- 12.6	- 11.6	- 10.6	- ten
- five	- 18.7	- 17.2	- 15.7	- 14.45	- 13.2	- 11.95	- 10.7	- 9.9	- 9.1	- 8.3	- 7.5	- 6.7	- 5.9	- 5.4
0	- 14.5	- 12.9	- 11.3	- ten	-8,7	- 7.45	- 6.2	- 5.3	- 4.4	- 3.6	- 2.8	- 2.05	- 1.3	- 0.7
+ 5	- 10.5	- 8.9	- 7.3	- 5.8	- 4.3	- 3.25	- 2,2	- 1.1	- 0,1	+ 0.75	+ 1.6	+ 2.45	+ 3.3	+ 4.1
+ 10	- 6.7	- 4.95	- 3.2	- 1.75	- 0.3	+ 0.95	+ 2.2	+ 3.2	+ 4.4	+ 5.4	+ 6.4	+ 7.3	+ 8.2	+ 9.1
+ 15	- 2.9	- 1.05	+ 0.8	+ 2.4	+ 4	+ 5.35	+ 6.7	+ 8	+ 9.2	+ 10.2	+ 11.2	+ 12.15	+ 13.1	+ 14.1
+ 20	+ 1	+ 3.1	+ 5.2	+ 6.95	+ 8.7	+ 10.1	+ 11.5	+ 12.8	+ 14	+ 15.1	+ 16.2	+ 17.15	+ 18.1	+ 19.1
+ 25	+ 5.2	+ 7.45	+ 9.7	+ 11.4	+ 13.1	+ 14.65	+ 16.2	+ 17.5	+ 18.8	+ 19.95	+ 21.1	+ 22.05	+ 23	+ 24
+ 30	+ 9.5	+ 11.7	+ 13.9	+ 15.8	+ 17.7	+ 19.5	+ 21.3	+ 22.5	+ 23.8	+ 24.95	+ 26.1	+ 27.1	+ 28.1	+ 29

Humidex relative humidity calculations

		Temperature, ° C
		21	25	thirty	31	32	33	34	35	36	37	38	39	40	41	42	43
Relative humidity,%
	20	-	-	-	-	-	-	-	-	-	-	40	41	43	44	46	47
	thirty	-	24	31	33	34	36	37	38	40	42	43	45	47	48	50	51
	40	-	26	33	35	37	39	40	42	44	45	47	49	51	53	54	56
	50	22	28	36	38	40	41	43	45	47	49	51	53	55	57	-	-
	60	24	thirty	39	40	42	44	46	48	50	52	54	57	-	-	-	-
	70	25	32	41	43	45	47	49	51	53	56	58	-	-	-	-	-
	80	26	34	44	45	47	50	52	54	57	59	-	-	-	-	-	-
	90	28	35	46	48	50	52	55	57	60	-	-	-	-	-	-	-
	100	29	37	48	50	53	55	58	-	-	-	-	-	-	-	-	-

Notes

↑ City error sends sewage into Winnipeg basements - Manitoba - CBC News

Links

Frequently Asked Questions , MSC, 2004.
Wind chill and Humidex Criticism about wind chill and humidex
More Humidex info

[1] City error sends sewage into Winnipeg basements - Manitoba - CBC News