Cold weather and the SOC

I noticed something interesting during the recent cold weather. With my short commute and the engine running longer/more the SOC is much higher than it has been. It frequently sits on the top blue bar or the first green bar. Today it warmed up to the mid-60's and the SOC went back down to the "normal" mid range.

It is supposed to get much colder tonight so I'll see if it goes back up.