I really think it's what you're used to. I have an intuitive sense of what temperatures from around -25 to +40C feel like (roughly the range I've experienced,

I really think it's what you're used to. I have an intuitive sense of what temperatures from around -25 to +40C feel like (roughly the range I've experienced, plus a bit), and nearly no intuitive feel for a temperature in Fahrenheit without conversion. Also, it's really not possible to differentiate between air temperatures with a difference of 1 degree C. Water temperatures maybe, with practice, but certainly not to a greater precision than 1 degree. So I'd say precision beyond that degree is wasted!