Ok, that might be a slight exaggeration. Something like a tornado would probably qualify as bad weather. However, if the weather is not threatening your very safety, I would go so far as to say it is good weather for landscape photography, rain, shine, or anywhere in between, and this great video demonstrates why.
Coming to you from Henry Turner, this awesome video shows that no matter what the weather, you can make worthwhile landscape photographs. I think this is something that does not get discussed enough, and that is a shame, as you might be missing out on great images if you only shoot when conditions are ideal. The important thing to remember when you head out in potentially inclement weather is that you are not going to come home with the same shots as you would during a beautiful, partly cloudy day. You have to change how you find potential in each scene you encounter and create shots that the conditions are conducive to rather than trying to will that sunny day shot into existence through editing or the like. Once you rework your mindset, you will find that you can create just as many compelling photos. Check out the video above for the full rundown from Turner.
And if you really want to dive into landscape photography, check out "Photographing The World 1: Landscape Photography and Post-Processing with Elia Locardi."