If it were me....
For safety & security, I wouldn't leave any loaded firearm in a vehicle, 24-07, or year round. If you really want to tote a sub-compact Glock pistol, I'd store it in a excellent Bore-Store bag, with a light amt of a high quality CLP like Weaponshield, Gunzilla or Mpro7's LPX. Apply the CLP at least 2 times a year to the areas listed in the Glock's owner manual.
If you are going to use the motor vehicle & have let the pistol sit in extreme cold weather, I'd unload it & conduct a quick function check before you take off, to make sure the sub-compact works correctly.
You'd want to know your Glock works BEFORE you may get into a critical incident.
I'd read years ago, that many spec ops units or troops would test fire their weapons on the helicopters while en route to a mission. They didn't want anything to bust or break down during a firefight.
Every 2nd matters.