Jeff, as Eskrimast1 stated, keeping the windows cracked open may help keep the IMA battery and power control module cooler. The power control module will be operating in a very limited fashion to protect the batteries as well as itself. This is clearly mentioned in the 2006 HCH Service Manual.

My solution was to purchase one solar powered window vent. Basically you simply hook this device on the driver's window, roll the window up until it closes, and it will promote airflow between the cabin and the outside of the vehicle. This thing works so well, that I am going to purchase one more for those moments when the vehicle is at a beech in a blistering hot day.

Here's an example of a device similar to what I have.

Cheers;

MSantos