# Can a humidex indicator be added under the humidity. This can be a very useful piece of weather information

Asked by mttr on 2010-07-31

How is the humidex calculated?
A.

The Humidex formula is based on the work of J.M. Masterton and F.A. Richardson at the Atmospheric Environment Service (now MSC) of Environment Canada in 1979. It is a standard for Canada, but variations are used around the world. The dew point temperature should be given in kelvins (temperature in K = temperature in °C + 273.16) for the formula to work. The magic number 5417.7530 is a rounded constant; it's based on the molecular weight of water, latent heat of evaporation, and the universal gas constant.

e = vapour pressure in hPa (mbar), given by:
e = 6.11 * exp [5417.7530 * ( (1/273.16) - (1/dewpoint) ) ]

h = (0.5555)*(e - 10.0);
humidex = (air temperature) + h

from Environment Canada web site

## Question information

Language:
English Edit question
Status:
Solved
For:
Weather Indicator Edit question
Assignee:
No assignee Edit question
Last query:
2010-07-31