Metric translation because it's am*ricans who don't put in the unit and it's am*ricans who take an am*ricentric view to everything:
16°f = -8.889°C
38°f = 3.333°C
.
Seriously just use metric and put the am*rican units in brackets or a translation note
Its not that hard.
... what are you on about? These characters are in Japan, and they're already using Celsius. 38°C is maybe a bit too warm imo to be considered a "lukewarm bath", but 38°F is damn near freezing and would quickly cause hypothermia; it would make no sense in this context.
Seriously, if you're at the point where you mistake numbers given in your own measurement system for another AND you can't even recognize how out of place the measurements are after you've incorrectly converted them back to Celcius, you should probably do soul searching on why you have such an irrational hate boner for Americans.
Sincerely, an American who can, believe it or not, understand both Fahrenheit and Celcius and doesn't mind that Celcius is the default in manga scanlation.