Frost on *inside* of Windshield

I read through this old thread -trying to figure out the frost daily inside my windshield, on our 2013 Prius.
I guess I'll try making sure I don't use recirculation mode. The other thing I realize reading here, is that maybe the Weathertech mats, which in winter are usually wet from melted snow, that's probably a big source of moisture in the vehicle. I'll report back if I'm able to address it these ways.

 

Do drain or empty those mats outside the car. Be sure to check under them too, for any spilled moisture. And look around for any damp clothing or other reservoirs of wetness, get them out.

Be especially watchful of any towels or rags used to wipe down the windows. They should be removed nightly, dried somewhere else, otherwise the very same moisture wiped off today will evaporate overnight and be found re-coating the windows tomorrow morning.

 

Here is my solution to inside window frosting. Yeah, never use recirculation on HVAC. The key is to reduce moisture inside of the cabin. You can also try anti-fog (or shaving cream) trick on the window. It really works.
Internal Frost Accumulations on my 2020 Prius Prime | PriusChat