As I enjoy the dichotomy of Vancouver - there's snow on the ground but all my spring bulbs are coming up and it's not yet Christmas - I recognize a similar conflict within me. During this peaceful time of year, I'm getting images of people pushing each other's buttons to the extent that it's guaranteed someone will be murdered.
That's the easy part: deciding who will be murdered and by whom. That leads to the motive or the "why" of the tale. Then comes the fun part: the "how" it gets done. From there, it's a matter of laying out the bread crumbs so a reader hears the story while also having an opportunity to figure out "who done it". It's all in a way playtime.
And isn't that what the season is for: having fun? So I guess it is also a time for murder (at least in a crime writer's mind)!