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Frost on INSIDE of windshield

2007 Toyota Prius - Never had a problem like this the first 2 winters I had this car. Have had a few episodes in the past month where the outside of the windshield is dry and the inside has frost. One time previously, the frost on the inside was so thick, I could have used a scraper for several minutes. I’ve checked every window and door and there seems to be no leaks at all. Another time, outside of windshield was dry and inside had a ton of condensation. Any ideas ??

too much moisture inside of car…open windows to let out moisture…run defroster and AC to reduce moisture… reduce moisture in car by shaking snow off boots and dry car mats if you can…

Most situations like this are the result of the driver operating the HVAC system in the recirculation mode. In addition to causing fogged and frosted windows, this is also the way that people become asphyxiated if there is even a small leak in the exhaust system.

If the HVAC system is not being operated in recirculation mode, then the other possibility is that excess moisture is being introduced into the car by wet/snow-covered boots and shoes. Make sure that you scrape as much snow off of your footwear as possible after you sit in the car, and while your feet are still on the ground. And, as was also suggested previously, be sure to operate the defroster/AC in order to dry out the air in the car’s interior.