This Internet research activity has students looking at different points on the globe and finding out about weather in that area. I like the grid that this activity uses. You could also integrate this into an Excel activity.
This website has 5 games to teach the weather. It starts with an activity that has a world map on the wall. I think that every classroom should have a world map, particularly if you're going to collaborate globally. Once a student knows another student from somewhere, it is incredible how that point on the globe becomes real.
If you want to teach students about hemispheres and weather, this powerpoint is a place to get started. Interestingly, many students don't understand that seasons vary by hemisphere until they collaborate globally. If your students are collaborating cross-hemisphere this is a nice powerpoint to use to get started.