First time I've gotten this text message but probably normal for our northern friends. But it's my first winter with the Bolt.
OnStar: Weather forecast predicts temperatures cold enough to immobilize your vehicle. As a precaution, always keep your vehicle plugged-in when not being driven.
Sent to me at 8:15pm last night. It got down to -1 F as the low last night (-17 with wind chill). Maybe 0 degrees is the cutoff because it's been down to single digits a couple days this winter. I trade garage spot with my daughter depending on who leaves earlier but based on info I've come across I do plug it in if it will be below the freezing point or snowing so I can precondition once or twice. I have hilltop reserve enabled when home.