It also depends on what you're doing. Id I'm going outside and do something (even just going for a walk) I'm gonna start wearing shorts and t-shirt at around 17°C. If I stay inside playing video games and barely move at all i might wrap myself in a comfy blanket or hoodie even a bit above 20°C (especially with open windows and a nice breeze).

You should buy them some fun headbands as a gift! I'm in the colder sample set and I wear headbands all the time. So does my son. They're super functional.

If I get much over 72°F I start dying, will be comfortable down to about 65°F and then it's creeping into too cold.

Crazy how humans be like that.