Weather

[SekoETC]

1. weather affecting effectiveness of farming - Maybe, although it's not completely necessary
2. seasons - Yes, but it would be good if they spanned several years like in Game of Thrones, like Doug mentioned
3. seasons affecting effectiveness of farming - Yes, and even better if different islands have different strengths of seasons. If some islands had long winters and short summers, it would make sense to import food from the tropics.
4. temperature - Yes, descriptive
5. Wind - Yes if 6 applies, otherwise it's pretty pointless
6. Wind affecting speed of sailing ships - Yes, this would be cool
7. Public event in location when weather changes - It would get tiresome if it changed every day, so it would probably be enough if it was listed on the location page.