Anwer: I would say that you have a thesis it's just that you could add more detail to it.
This is what I would say:
It was a cold, dark Saturday evening. I was reading my favorite book (enter here), when I heard sirens wailing outside my house. I got up from the couch, curious to see what was going on.
Extra Notes:
I would also add on to your story about about what you saw outside of your window.
