Fortunately my wife is both gracious and adventurous in this regard, and is cool with having most of our stuff on Celsius. I switched before we were married, and she’s slowly learning by virtue of everything being on Celsius except her phone.

Edit: Also, this may be helpful, I came up with a heuristic early on to approximate Fahrenheit values to help me learn.

I memorized every 10 (and eventually every 5) and then approached from the nearest memorized point using 2°F per 1°C instead of 1.8.

For example, if something said 22°C, I’d start at 20°C=68°F and work my way up, adding 4, to get to 72°F. Since the actual value is 71.6°F, that’s close enough.

If you forget a 10 or a 5 it’s easy to recalculate them if you know another, because it’s 9°F per 5°C. So if 20 is 68, and 30 is 86, then 25 is 77.

(Obviously you could also do the full conversion but that takes me more time.)