It's definitely not cold related. It's happening on my 2017 Outback here in Southern California where it's currently 85 degrees (Fahrenheit!). I thought it was something I did wrong.I am ave started noticing the same issue for the last few weeks. I own a Subaru Outback Limited 2016. Sometimes even if I shut off the engine and sit inside the car for 10-15 seconds and then open the door, I am hearing the same alarm. This is happening in totally random fashion. It sometimes get really cold here in Edmonton, Canada. I am not sure if this issue is anyway related to the cold temperature.