I had an unusual experience travelling home yesterday evening. It was still quite warm so I had the aircon on in the car, but the windscreen was slowly misting up. I increased the fan speed which only made it worse . . . until I realised the misting was on the outside, caused by a combination of the high air temperature and humidity and the chilling of the 'screen by the air conditioning. A burst of warm air from the heater dispersed it quickly, but it's something I have never before experienced in 50 years of driving. Maybe I never had such an efficient air conditioning unit before 
Not really model engineering but perhaps a good illustration of the 'dewpoint' effect which causes rust on machines and has been discussed on the forum many times.