As you mentioned correctly: if you go for strongly typed types in a library you should go all the way.
And that means your strong type should provide clear functions for its conversion to certain other types. Some of which you nearly always need like conversion to a string or representation as a float/int.
The danger of that is of course that you provide a ladder over the wall you just built and instead of
They now go the shortcut route via numeric representation and may forget the conversion factor. In that case I'd argue it is best to always represent temperature as one unit (Kelvin or Celsius, depending on the math you need to do with it) and then just add a .display(Unit:: Fahrenheit) method that returns a string. If you really want to convert to TemperatureF for a calculation you would have to use a dedicated method that converts from one type to another.
One thing to consider as well is that you can mix up absolute values ("it is 28°C outside") and temperature deltas ("this is 2°C warmer than the last measurement"). If you're controlling high energy heaters mixing those up can ruin your day, which is why you could use different types for absolutes and deltas (or a flag within one type). Datetime libraries often do that as well (in python for example you have datetime for absolute and timedelta for relative time)
The danger of that is of course that you provide a ladder over the wall you just built and instead of
They now go the shortcut route via numeric representation and may forget the conversion factor. In that case I'd argue it is best to always represent temperature as one unit (Kelvin or Celsius, depending on the math you need to do with it) and then just add a .display(Unit:: Fahrenheit) method that returns a string. If you really want to convert to TemperatureF for a calculation you would have to use a dedicated method that converts from one type to another.The unit thing is of course an example, for this finished libraries like pythons pint (https://pint.readthedocs.io/en/stable/) exist.
One thing to consider as well is that you can mix up absolute values ("it is 28°C outside") and temperature deltas ("this is 2°C warmer than the last measurement"). If you're controlling high energy heaters mixing those up can ruin your day, which is why you could use different types for absolutes and deltas (or a flag within one type). Datetime libraries often do that as well (in python for example you have datetime for absolute and timedelta for relative time)