Funny -- I have not got below 4. Garage temp in AM is often under 40, but above freezing.
The one day, the starting outside temp was 12, and rose along the way.
The garage at TMC is unheated, but does protect from wind and elements mostly. Leaving temps were under 20 a couple times and I still was showing 4 bars, after sitting outside for 8-10 hours.
So, two theories: One is that perhaps the temp sensors are not that accurate.
Second is that my garaged battery maintains its heat long into the day. It probably heats up some with 16 miles of brisk driving (consuming 4 or more bars on a cold day), and slowly cools back down during the day.
Hard to say -- suppose more information could be gleaned from the forums, but hard to say.....