The lithium ion battery likes room temperature, just as we humans do. It is most susceptible to stress (through the Arrhenius reaction that all battery experience) when it is fully charged and hot; hence the thermal management, even with the car off. Once the charge level depletes (as it will when driven, or after running thermal management for a while), temperature is no longer such an issue. The sound level of the fan was designed "so it wouldn't wake a sleeping baby"
The good news is that your EV range has undoubtedly improved with the warmer weather. You are a bit warmer than Michigan; I was told at the Woodward Cruise event by a very senior member of the Volt engineering team that living in Michigan, without all the very hot parking lot soaks, I should be able to expect 16 years out of my lithium ion battery.