What gets the ball rolling is the sun: solar panels generate electricity as long as photons of sunlight strike the solar cells
. If it shines when it's boiling hot, so be it. If it shines when it's freezing cold – even better! In fact, when it gets over 90 °F, solar panel efficiency starts to decrease at a rate of 1% per degree. So, it turns out that PV modules perform best when it's sunny and cold.
Such an advantage of winter months is offset by the fact that the days are shorter, which means less peak sun hours. What's more, in some states it snows heavily in winter. Snow is one of the factors which influence solar panel efficiency
, so let's see how big this impact might be.