In one of my now destroyed polar playthroughs, I noticed that during winters and cold snaps, I always got mechanoid raids. Was that just my constant bad luck, or does the game not send human raids when it hits a certain temperature threshold?
IIRC it bottomed out at around -60°C during the middle of winter, which on paper should be survival for pirate raiders in parkas, less so for tribals.
Tribal raids were rare; getting serious hypothermia by the time they got the killbox, hah!