The familiar part has changed for Canadians.

I grew up during the transition period I was too young to know Fahrenheit, I had just entered school when the switch was occurring.

My parents are pretty well used to Celsius now but still may occasionally use Fahrenheit such as some electronic device that allows F or C they choose F.

It's still a but messed up though since Canada borders the US. The old joke being weather reports that show the border with the US say Detroit shown as 90 and Windsor as 32 "See Marge as soon as you cross the border into Canada it goes dow to 32!"

But still you get people of all ages saying things like "300km/h wow that's nearly 200 mph" or "You weigh 70kg what's that like 150 pounds?". It's more due to history and the influence of the US on our culture, I bet more french speaking areas like Quebec, northern NB don't do that but who knows maybe they do.

I was born and raised in Florida. I now live in Sweden. Because of experience, I understand C pretty well between -15 and +10, and between +80 and +100 (Swedish sauna temperatures).

Between +20 and +50 I'm still more comfortable with 70F-120F. I also spent some time in Illinois, where I learned to understand the subzero range from -15F to 0F.

At LOX temperatures of 90K and below, I'm most comfortable in Kelvin. ;)

0°C - water turns into ice 100°C - water boils and turns into steam

-30°C and below - very cold weather +30°C and above - very hot weather

But the freeze/boil numbers are arbitrary as well only being true at sea-level. Where I live in Colorado, we're 1 mile (cough, 1.6 km) above sea level meaning those formulas are meaningless.

They aren't meaningless. Water boils at 95 C at your altitude - effectively the same temperature for all "common" usages. E.g. you'd still better not stick your hand into boiling water.

A <5% error for the zone that >99% of humans inhabit seems pretty practical to me. The freezing point is effectively identical.

iirc, water boils at 95C is around 5000m altitude, no one lives normally there - even La Paz is less than 4000.

Well its rather easy to make your own thermometer using the Celsius scale. Put quicksilver in a small glass tube and put it outside. When water starts to freeze mark the current position with 0. Drop it in boiling water and mark it with 100. Evenly distribute now 98 markings between the two existing ones and voila you have just made your own thermometer :)

Evenly distributing 98 markings is hard. Evenly distributing 64 is easy -- just halve the range six times. That's why the distance from freezing water to body temperature is 64 Fahrenheit degrees.

Except...

Freezing point of water: 32°F Average human body temperature (oral): 98.2°F

So that's 66.2°F, not 64°F.

Those two temperatures were the original reference points for the Fahrenheit scale, and body temperature was defined as 96°.

The current definition is relative to the melting point of ice (32°F), and the boiling point of water at standard atmospheric pressure (212°F, which is exactly 180°F higher than the freezing point). Except now body temperature is 98.2°F instead of 96°.

If you want a thermometer calibrated in Fahrenheit, you have exactly the same problem as you do with Celsius. You just have to put 178 markings between the two reference points, rather than 98.

I don't think its advisable to use my self-made quicksilver thermometer for any kind of body temperature measurement.

Which makes no difference because you're eyeballing it to start with. You can just as easily divide the 0-100 range in half a bunch of times. Your thermometer is not achieving <1 degree accuracy.

Of course if you have a tool to accurately measure halves, then you can also measure any other division you care to use.

All depends what you are used to - I would say 15C or so is "comfortably warm", 22C is definitely "warm" and 40C is utterly miserable with no wind but really nice with a breeze and in the shade....

People generally start sunbathing, wearing T-shirts and flip-flops, when the temperature goes above 10C here...