In ‘Fragrance of Violets’ the weather does contribute to the story. It’s set in the Lake District and I know from experience how often it rains there!
So one important scene takes place on the valley road in the pouring rain, and it’s the rain which causes the collapse of a roof which in turn leads to .. no, I’m not going to tell you the story here!
But there are also beautiful spring days in Lakeland when, after the rain, the air smells so fresh and clean, and the mountains and lakes look stunning, so my h/h can enjoy that too.
My current WIP (with the working title ‘A Nile Romance’) is of course set in Egypt where it’s hot in winter and even hotter in summer! There are blue skies and sunshine, beautiful sunrises and sunsets, and warm, clear inky-dark nights. Perfect for a romance (as long as you have air-conditioning, of course!) but not a lot of scope for using the weather, since it's the same all the time.
I’m not a fan of matching weather to the moods of the characters or the events in their lives. You know the kind of thing, you see it in so many movies – the ferocious storm before or during some traumatic event. Maybe a contrast between the weather and the characters’ feelings is more effective. A beautiful day when the heroine is going through hell at losing her man, or a dismal grey day when her heart is singing? In my experience, that’s probably more realistic :-)