I can save fine (it says saving... done!) and it doesn't crash, BUT some things doesn't save.
For instance:
I create a new weather by duplicating an existing vanilla one, change some things, edit the name, etc... and after that I go to the regions tab and delete all vanilla weathers in a region and add my weather to 100 % chance. Everything looks fine. I save, still fine.
Then I start the game and nothing... my weather doesn't start. Now here's the strange part, I reopen the CK and load my recently saved weather .esp, and guess what? The changes I made to the region are gone. The vanilla weathers are still in the region. My weather still exists in the objects window, but it isn't added to any regions. It's as if the CK has some big trouble properly saving information.
Note that this doesn't happen all the time. One time I actually succeeded in saving my weathers into a region (they still existed in the region when I reloaded the .esp). Other times the results were the same...
A big CK bug? This is keeping me back from doing my weather mod atm sadly. I'll just do cloud textures in the meanwhile...
Another problem is that I can't force any weathers I add. I can see the form ID in the object window in the CK, and I use the fw command in-game... but nothing happens, as if the weather doesn't exist (even though I can see it in the CK). Sigh.
Can anyone test this and see if it happens on your computer too? Just duplicate a vanilla weather and go into the regions tab, scroll down to the Weather regions at the bottom, then go to the weather tab and delete the vanilla weathers and add your duplication; my advice is to do this to both the WeatherTundra region and another region of your choice (on my tests it seems for some reason that the tundra region had the biggest problems saving... it never saved once). Save it to a plugin and then quit the CK and reload your plugin and see if it saves.