The environment and weather can act like characters in a novel. Their "personality" has to be consistent and the players have to interact with them and follow their guidelines.
If a writer puts in a description like, "She looked up and saw dark clouds fill the sky," the characters should be aware it might rain.
The important thing is for the author to write like they are walking through the story. Be aware of how the sun warms our skin, our heartbeat quickens as we walk down a bustling city block, or how we might flinch at the crack of thunder.
Yesterday, my protagonist left her friend's house on a stormy night. A short while later she was captured and forced onto a sail boat. Sail boats don't do very well in violent storms. I missed an opportunity to bring the "character" I created-a tumultuous storm, into the drama of the scene. When I went back to edit it, I found several opportunities to capitalize on how the atmosphere conspired to create the horrific predicament she was in.
Our environment and the weather affects the way we feel and behave. In writing, they are crucial factors to consider and will help develop the story.