Timelapse problems outdoors - UV filter frost

[Jawa Ex Machina]

I recently bought a new Hoya UV filter for my canon 16-35mm L glass, and I've been getting into doing some time lapse stuff with my 7D because we've got great winter landscapes here.

I've been having problems though with frost covering the filter after about an hour outside.
Anyone know what the reason for this problem could be, or if there's a good, easy and cheap way of avoiding it?

 

[klon]

have you been giving your time adequate time to cool down? The temp gradient could be causing condensation that freezes.

 

[Jawa Ex Machina]

have you been giving your time adequate time to cool down? The temp gradient could be causing condensation that freezes.

When this happened I had it set for one 10" shot every 15 seconds I think.

But if the frost was caused by condensation from the camera, would it only be on the outside of the lens filter?

I'm thinking maybe the air humidity was high that day? Is there a way to treat filters to prevent this?