One winter, when I was young, I started paying attention to the thermometer that was set just outside the sliding glass door. I would look at the temperature it gave, and make a mental note of what it felt like outside. Pretty soon I had a good idea of what the temperatures felt like -- in Celsius.
You see, no one had told me "In the USA we use Fahrenheit, not Celsius, so you can just ignore the temperatures that have a little c next to them." That being the case, I just went with what seemed natural to me, which was freezing being equal to zero. I don't know how I learned my mistake, but I know I became enlightened soon enough. Yes, when the weather started warming up, I started looking at the numbers with the little f next to them.
The result is that I find myself in an interesting predicament; I know my colder temperatures in Celsius, and my warmer temperatures in Fahrenheit! Really, it is quite strange. The cut off point where I switch from one to the other is 20*C, which is 70*F. (Ok, so it's actually 68*F, but I figure 70 is close enough. :P) So in the summer I have no trouble following what people are saying about the temperature, but other times of the year things can get...interesting.
I am learning to recognize the lower temperatures in Fahrenheit. I've always known that 32*F is freezing, and of course I know that 70*F equals (approximately) 20*C, so that's a help. I also have a little thing I printed off the Internet taped to the side of my monitor, which helps me "translate" between the two.
Then Tall One insists on using Celsius because it's what makes sense, so I'm hearing all about the heat in terms of Celsius from him right now. That's also somewhat educational. "It's supposed to get up to 40 degrees tomorrow!" That's 104*F, by the way. And of course, I know that thanks to the thingy taped to my monitor. :) I hardly ever pay attention to it, but when I do, it's quite helpful.
So, I'm learning. But at the moment I have one foot in one world of Celsius, and the other in the world of Fahrenheit. Hopefully I can combine the two, and eventually switch easily between them whether we're talking hot or cold temperatures.