Here is a modified version of weirdgirlinkorea's PPT (there were a few pics missing that I added).
As I was about to start this lesson I discovered oh hey, we only teach the odd numbered lessons (another teacher does the rest). No, in 6 months of teaching together my co-teacher had never bothered to explain this. It had only come up once before (believe it or not - we work slowly!) and that lesson was the Weather one, so it made sense to skip it, I thought. TURNS OUT...Sigh. Anyway.