Whenever it rains, I get sleepy/lazy, not that that's a bad thing. For some reason, during these times, I turn off the TV, any music, and just listen to the rain fall. It's quite calming actually.
Also, I get visions. Maybe not visions but something similar. A powerful scene catches hold of me and makes me just sit and write it out. I see every detail of it. The room, the people, and the dialogue. If I don't pay attention to it then, I lose it and on occasion, it'd be the scene I needed the most.
Right now for instance, I'm trying to write this post as quickly as possible so I don't lose it. Have you ever been somewhere odd or in the middle of a conversation and had a powerful scene hit you??