I still recall watching some science/nature program where a scientist is talking about the extreme conditions they had to deal with and says it was "minus 40 degrees" and then, after a short pause, adds "Celsius". It still makes me chuckle just a little.
My girlfriend from Texas now living with me in Canada has had me translate very quickly in my mind between C and F. Same thing for kilometers and miles.
I was camping in the mountains last weekend and gassing up at a tourist spot. Someone asked "how many litres in a gallon". I yelled out "3.8". Then they asked as a joke "how many kilometers in a mile?" ... "0.6". As they drove by me leaving the parking lot they were smiling, and they asked "it's 14C right now, what's that in F?" ...it takes me a few seconds to calculate, and I said "about 56".
It was a cute moment for myself and the people who were visiting from California.
My car is from Canada, so i got used to some conversions. (The mph markings are too small for me.) When i need 55, i go 90. When i need 25, i go 40. I don't even need to look at the conversion cheat sheets taped near the speedometer as often. The speedometer itself is off a bit and seems moody, which allows for some needful guessing.
More recently, i downloaded a speedometer app for my Android, which works great outside of tunnels. As an odd side affect, i was shifting gears about every 20 kilometers on the speedometer (not the odometer!) and based on sound. With the phone covering most of the speedometer, i rely completely on sound.
Next time i'm in Windsor, it's just going to be weird.
The primary vehicle I drive is from US so we're in the exact opposite situation :). Everything is miles, and like you, I find the km portion to be too small.
We drive all over the place regularly (from Calgary to Dallas, and back, as well as across Canada), so I bought a cheap North America GPS ($99). I switch it from miles to km and vice-versa depending where I am, and it allows me to see exactly my speed without needing to look at the dash at all. it also warns me in a different colour if I'm going 5km+ over the limit, or 3m over, and even alerts on red-light cams.
Celcius is the scale used in my country, but the thermostat of the air conditioner system at home failed, and the only replacement piece available for that model was in Fahrenheit. I had to print a table with a conversion scale and place it at the side of the control unit.
For air temperatures outside, I've always known and preferred C, but in my greenhouse and grow rooms I much prefer F (as that seems to be the standard in almost all literature I read and the groups I belong to).
I prefer degrees F because I grew up with it and therefor think in terms of weather(comfort or lack thereof). If I am working, however, I prefer degrees C (and metric in general) for obvious reasons....
...the majority is always wrong, and always the last to know about it...
A solution is nothing more than a clearly stated problem...