Sure, but with a couple inches of snow on them, mine still generate power. And in areas which regularly receive snow, roof pitches are generally steep enough to encourage it to slide off else the building would suffer overloading. Worst case a push broom or squeegee with a very long handle works wonders.

Also fairly trivial to rig up a resistive heating system for melting the snow in cases where the above isn't possible. Even possible to automate it based on time of day and expected power input.