Although It was a dark and stormy night is considered one of the worst opening lines, I think weather can be very important. Think about the hobbits on their way to Mordor, bearing the greatest burden of all time. Of Weathertop, Frodo got lashed with rain while fighting off the Nazgûl. That scene would have been much less effective if the action had occurred in daylight under sunny skies.
So for today’s prompt, play around with weather in a scene. Can you alter the mood by altering the weather? Can you reflect a mood in the weather? Use weather as a counterpoint? A jarring note in your scene–something not quite what the reader would expect? How does it work to have rain in a happy scene? Blue sky and sun in a battle to the death?