Check the terrain files on your hard drive.
Any terrain.res file with a matching .awa file has clouds. Whether or not there are "lots of clouds" will partly depend on how long you leave your offline room up. It can take an hour for the clouds to build, it's a slow process.
If you find a cloud file you like, you can copy and rename it to a different terrain file, but the clouds might not be where you want them.
Those are the quick approaches, any terrain can have a cloud file added, and that info is available in the help files.