Thanks for the feedback.
I spent last night with different thermometers trying to get a repeatable reading. I was using those small digital thermometers that read both temperature and humidity. This morning I went out and bought a Taylor fridge/freezer thermometer (after checking that it read the same temp as the other 5 thermometers on the shelf). It reads 37F. I put a glass of water in the fridge beside it and gave it a few hours to cool. My
Thermapen also reads 37F in the glass of water so I finally have a repeatable reading that gives me some confidence.
Come spring I'm going to have to turn my fridge down cooler again.