Its called common sense and homework. Just got back from Moab area doing some winter hiking, great times saw nobody, and it was cold.
Weather was not as cold in Green River but still well below freezing at night. Daytime temps were in the 30s down to the teens. Nighttime temps were in the teens to single digits and have been all month, even below zero. Good to hear he got out ok. Water freezes at 32 F, at least thats what I learned in grade school.