The brake squealing probably has nothing to do with the parking brake. The squeal is there in cold and rainy weather because your car doesn't have the shim + grease kits installed which take care of most of the noise. The rear brakes make the most noise without those kits. No 2012 vehicle was originally built with the shim kits.
The parking brake ECU is unfortunately resetting on your car, which could be due to disconnection of 12V or a ground issue, or the cable itself is getting stuck. The low VIN vehicles had a ground strap added in the front right kick panel that often is intermittent. You would need an ability to read the park brake ECU fault codes to see what's going wrong.
Vehicles stored for a long time with the park brake applied (ie, unsold at a dealer or at a port for months and months) often have damage to the nylon coating on the park brake cable at the back of the car, the rear cable attached to the park brake actuator motor. This nylon coating has been seen to get a bit chewed up if it sits at full tension. Then when the motor disengages the cable, the cable strand doesn't go back into the conduit housing and gets stuck. At that point, the ECU recognizes that the park brake didn't fully disengage, and it tries again to retract fully (you will hear it click a bunch of times as it goes to full retraction) and then disables itself. You can peek through the rear fascia valance and see if the cable strand plastic coating is damaged at that point.
If I were to bet, I'd suspect the cable. You don't actually need a new one... just need to trim off the damaged nylon around the strand and it should retract smoothly. The fascia will have to be removed to see it. It's an easy fix.
The moral of the story is don't park your car for a year with the park brake applied.