# Humidex Value

Brian, in Canada, Environment Canada has a measure of humidity and temperature called the Humidex. It’s similar to windchill. I compared the heat index against humidex and it looks like it’s calculated differently. Any chance you could include humidex for Canadians?

Here’s what I’ve found for humidex:

Humidex:

Humidex is a calculated parameter which is based upon temperature and humidity. It gives a measure of the amount of discomfort felt by the combined effect of the above two elements. We use the following formula to calculate Humidex:

Humidex = T + 5/9 * (e-10)
where:
e = vapour pressure(6.11210^(7.5T/(237.7+T))*H/100)
T= air temperature (degrees Celsius)
H= humidity (%)

can you give an example so i know i have it correct

Not sure I want to step near another of these index things, but you can use the online humidex calculator at;

Here’s another formula:

Humidex = (air temperature) + h
h = (0.5555)*(e - 10.0);
e = 6.11 * exp(5417.7530 * ((1/273.16) - (1/dewpoint)))

If T=25.4C and the Dewpoint is 10.8C (you must convert the dewpoint to degrees Kelvin 283.9K)

Then e=6.11exp(5417.7530((1/273.16)-(1/283.9)))
e=6.11exp(5417.7530(0.0036609-0.003522)
e=6.11exp(5417.75300.0001385)
e=6.11*exp(.7503)
e=12.939

h=.5555*(12.9-10.0)
h=.5555*2.9
h=1.632

Humidex= 25.4 + 1.632
= 27.0

Whew!!

i have added this new formula next to the humidity in the default web table in a new 9.83d, ready now (as a start)

Brian, in Canada, Environment Canada has a measure of humidity and temperature called the Humidex. It's similar to windchill. I compared the heat index against humidex and it looks like it's calculated differently. Any chance you could include humidex for Canadians?
You may like to look at: http://www.industrialsourcebook.com/cgi-bin/archivef.pl?id=368

You may like to contact the number listed at the end of the above document to see if they have reached a conclusion.

I will stick with WD’s MDI for now.

As for Heat Index vs Humidex, I’ll stick with Humidex.

Why?

Since Environment Canada uses the Humidex value in their public forecasts, myself and my family (and probably most Canadians who rely on public weather forecasts) have grown accustomed to this measure of heat discomfort. It’s like metric vs imperial. My website shows metric vaules since most people looking at it are comfortable with metric.

Heat Index might be the better indicator but most people around here are more comfortable with Humidex.

Brian, would it be possible to select either Heat Index or Humidex on the summary image?

grab a new 9.84 now and tick that option in the summary image setup

Sorry to hear you have the flu, one thing after another huh?

How will custom tags work with the autoswitching wind chill/heat index?

You da man. I can’t believe the support you offer.

I guess my last request would be an html tag so I can include the humidex in my custom email report.

Thanks.

%humidexfaren%…Humidex value in oF
%humidexcelsius%…Humidex value in oC

in a new 9.84, ready now

Thanks again, I’ll stop bugging you now and let you get on to important stuff.

Brian, I updated to 9.84 last night and got the humidex to appear on the summary image.

I checked the webpage in the morning and it had changed back to Heat Index.

I updated to 9.84a and now neither show up on the webpage.

I’ve unchecked Humidex to see if Heat Index would reappear but it’s still mia.

Steve

mine also switches from humidex back to heat index and the heat index is about 10 degrees higher than what it should be.

the calculation value I am seeing is the humidex, which is correct, but the tag label humidex keeps switching back to heat index and that is the problem. It doesn’t stick.

Nice feature !!!

On a program restart or computer reboot I would like for the Summary Image humidex/windchill (or heat index) option default to the option that was ticked before the restart. As it is now (WD v 9.87) the Summary Image always displays the humidex option after a program restart or computer reboot. I have to change the option to windchill (or heat index). This started when the humidex option was added.
TIA