One of the first things I do every morning is check the weather; not only by looking out my window but by watching the weather on the morning news. Weather affects everything; what I'm going to wear, whether or not I'm going outside, what I'm making for dinner, to name a few. But, how often do we use weather in our books?
I admit I don't use it as much as I could.
People stuck inside because of inclement weather can lead to all sorts of interesting situations. A beautiful summer day is the time for picnics or rowing on a lake. People slow down in hot weather; there's always time for a cool drink or an extra ten minutes of conversation. On the other hand, hot weather can cause temper flare-ups; not many people are agreeable when they're dripping on the floor from the heat.
Imagine sticking your main character on a deserted road in a car that's run out of gas on a summer evening. Now imagine the same situation in a raging snowstorm. Which is the more threatening?
Windstorms cause power outages; always fun. Snowstorms isolate people; there's a reason Agatha Christie used them! Horror is always worse when it's juxtaposed with beautiful weather; sunny days are supposed to be happy days. But that's not always the way it works...
I'm not suggesting placing every mystery on a 'dark and stormy night'; but indications of the weather place our characters in the real world. Real people curse when it starts to rain and they've forgotten their umbrellas. Strangers become more talkative while they're waiting out a storm in a cafe. People get crabby when their feet are wet or cold. Everyone's lives are affected by the weather; shouldn't our characters be the same?
Take a moment and think about the project you're working on now. How would it change if you mentioned the weather? Or does it already play a large role in your plot? Make it real; let your characters get hot and crabby or shiver beside the fire. I think it adds another layer of reality to any story; regardless of genre.