its likely that he pollen filter is wet. not uncommon if its not been correctly covered or watrer drain holes in the scuttle panel area are blocked.
fyi The interior fan draws air in from outside under the bonnet near the windscreen and the pollen filter can be found there. Its stops leaves, crap and all manner of things being sucked into the car when you turn your fans on.
Not many people appreciate that water that flows down the windscreen runs under the bonnet and drains via drain holes inside the wings / near the end of the scuttle panel. This can get blocked by leaves or the like which can lead to the pollen filter (which is located nearby) getting soaked. (or as above due it being fitted incorrectly).
If the pollen filter is wet then as soon as you turn on the ignition air is drawn through the pollen filter and as a result damp/wet air is blown onto the windows, and due to the glass being cold and dew point temperatures (basically as air reduces in temperature so does its ability to hold moisture) the moisture in the air condenses on the surface of the glass.
Much the same as when you breath onto glass in the winter.