It is not uncommon to come by a question involving some use of units. Either it's temperature, distance, shoes sizes or any of the other countless cases where units are used. So the question is:
How do we best work with units?
Should it be US Customary, SI or a mix?
There are many things to consider, but I think it will be better to choose one "standard" and go with that. It makes it easier for askers and editors when there is an agreement on the correct way to write units.
I think having a combination of metric and US Customary is the most useful. It could be as following:
Water freezes at 0° Celcius (32°F) and boils at 100° (212°F).
We walked 100 km (62.14 miles)
I brought 10 liters (2.64 gallons) of water
I propose that the metric unit is first, because it probably is the most commonly used measuring system. The exact details of degrees, spacing and writing of unit could be left to the style appropriate in the situation.
Degrees are a particular concern. Degrees should ALWAYS have either °C or °F after them to avoid ambiguity - unless it's a compass bearing!
And, while the phrase "below freezing" is unambiguous, "sub-zero" is regularly used with both scales to mean unsurprisingly different conditions. I feel that should be replaced with "below 0°C/F" as appropriate.
Gallons and pints can be ambiguous too, but UK 'imperial' measures are only 'the norm' in a few special cases, like vehicle MPG in the UK. The rest of Europe uses l/100km.
