I got in my car this morning, about 13 hrs after last driving it last and leaving my driveway I noticed the temp guage already reading about one third up the scale. I remember reading something about the TCH having a storage bottle for keeping the coolant warm for faster warmups but I didn't think it would last that long (although it was a warm night last night).

Just wondering if that is a typical experience for others?

I thought the Prius had that storage bottle, and the TCH did not.

Maybe so, I've read so much stuff now it's hard to remember what everything applied to. I spent some time searching under the hood and it has two separate but ordinary plastic coolant tanks. One is definitely for the ICE, but other is on the other side where the electric motor n stuff is. Not sure if they interconnect or it's two completely separate systems.

I know that the outside temperatures are warm, but it seems to me that my TCH's temperature gauge is in it's normal range very quickly, probably less than one minute.

I believe the second coolant tank is for the invertor cooling system. It is listed in the owners manual on page 348. Shows both systems