This is the end result of being unhappy with the two Weather Icon sets on Cydia. I wanted a look more like the default UI on my iPod so I took some time and try and make a decent set of icons.
Extract Weather Icon.theme to \Library\Themes on the iPod or iPhone and enable it though Winterboard. You need to download Weather Icon from Cydia in order for this to work as well.
The backgrounds to the preview are not static. They change depending on the time. I just put the backgrounds on them to show what it would look like.
I would put it on Cydia but I have no clue how. I will look into it later today after I get home. I just posted it on MacThemes.
The only thing that would need to be done to make it compatible with other themes is to change the two basic background icons. It would be weatherbg_day.png and weatherbg_night.png.
That white stripe is suppose to be snow but it does not look like it. I am working on alternatives for snow right now. I am also making clouds lighter because it looks like rain clouds right now. I want to tweak the thunderstorms too. Once I am finished I will stick it on Cydia. I posted this pretty much when I finished it on another forum. I didnt get a day to really use it to see how it looks on the iPod.