I have had these for a few years now and leave them out in all weathers with no problem as yet. The only place I can see it being a problem is in the electrics and these seem to be cased in a clear silicon.
I would however try and steer away from the glass type that I have and go for the ones that are like a print on metal (monocrystalline?) as these are less likely to get damaged and a lot lighter but more expensive.