I'm in south-eastern Canada. Just now I checked the temperature of the water from my city water company I measured it at 8C. The current outside temperature is -1C. The water couldn't be lower than freezing or pipes in homes would freeze.

I agree cold, hot, warm are all relative. Somewhat related I've seen people from hot countries worry about "cold weather". To them ~20C is cold compared to 35C hot day and was blamed to be the cause of colds and flu. Often perpetuated in movies and TV too a tired old trope. So yes to someone in a hot country a "cold" shower may be considered warm to someone from a cold climate.