sub-zero

air temperature, atmospheric temperature, ambient temperature

not ... at all

even if ...,...cannot

very, exceedingly, awfully / (before a negative form) not at all, at all, by no means

stern, grave, forbidding; dignified, stately / strict, unforgiving / tight, close, without gaps / harsh, tough, extreme, severe, hard to withstand (said of natural phenomena)

(rare, archaic) wondrous, miraculous, splendid, sublime / (rare, archaic) dignified, solemn, stern, noble, refined / (rare, archaic) beautiful, pretty

the way in which something is tightly packed or close together without gaps

going out

to go out