In Canada we have long harsh winters but July was REALLY hot this year! How hot? Let’s combine heat & humidity to determine the real temperature we feel.

(Excel file: Humidex-Headindex-formulas v2)

Humidex vs HeatIndex

Canada uses humidex calculation while the U.S. uses HeatIndex.

Humidex (short for humidity index) is an index number used by Canadian meteorologists to describe how hot the weather feels to the average person, by combining the effect of heat and humidity

The heat index (HI) or humiture is an index that combines air temperature and relative humidity, in shaded areas, to posit a human-perceived equivalent temperature, as how hot it would feel if the humidity were some other value in the shade.

Humidex & HeatIndex in Excel?

I found what appears to be the common formulas for Humidex & HeatIndex.

Let’s start with Humidex formula. You’ve seen a heat advisory but a formula advisory?

Formula Advisory?!

This formula is extremely long and tedious to read. It may cause dizziness, exhaustion, confusion, etc. Seek professional help if you feel any of these symptoms.

Simplify Formula step 1

By entering a few carriage returns we can isolate each nested IF. It’s a bit easier to read.

Simplify Formula step 2

Upon further examination I noticed that this part repeats several times:

(((-42.379+2.04901523*D4+10.14333127*C4-0.22475541*D4*C4-0.00683783*D4*D4-0.05481717*C4*C4+0.00122874*D4*D4*C4+0.00085282*D4*C4*C4-0.00000199*D4*D4*C4*C4)-32)*5/9)

I put it in a named range called ‘hx’. I also created named range ‘cnvt’ to convert Celsius to Fahrenheit.

The humidex formula below is now much easier to read!

You’ll have to also audit the named ranges but it’s worth it!

Now let’s look at the HeatIndex formula.

This is from Dick Kusleika’s Excel site. I can’t think of a way to make this easier to read, can you?

I definitely agree with Dick’s point below!

People have been complaining about the excessive heat for a week around here. Not me. It won’t be long until I’m shoveling my driveway, so I’m counting my blessings.

I’ve enjoyed this warm summer. Today (Aug 10) had a high of 23C, 41% humidity and a cool breeze 🙂 (much cooler than most days in July!)

After summer is nice fall weather. Then in the winter we will be complaining about the wind chill factor (maybe I’ll calculate that too!) and dreaming of hot summer days!

Heat Definition

What is your definition of heat? Many from the north of Canada consider southern Ontario summers to be unbearable. But those of you from warm climates would laugh at us in Canada. But then again if you visited Canada in the middle of our winter you would be in shock and we would know what to do 🙂

Further Reading

The overall “how we feel” calculations have different variations. Also, we all experience heat differently depending on our tolerance (i.e. health, age), intensity of our outdoor activities, etc.

Here’s some interesting info regarding working outside in the heat (Canadian government). My Excel file has various related links.

About Me

My name is Kevin Lehrbass. I’m a Data Analyst and I live in Markham Ontario Canada.

Right now it’s summer and it’s been hot (several 30C + days).

Our climate varies a tremendous amount from winter to summer. During winter the temperature can go all the way down to -30C (I live in the southern warmer part of Canada!) but usually it’s between 5C and -20C.

In winter we have to clear our driveways (or pay someone) but the city clears the roads and sidewalks. In Markham we don’t have to shovel the roof of the house but apparently in some parts of Canada that’s necessary. Here the temperature rises enough to periodically melt the snow on the roof.

I’m going to enjoy the last part of summer 🙂 being in my backyard without putting on a coat or shoes!