If you are using a mod that allows you to fire you guns in any kind of weather or adjusts StormCoditions you won't see the crew in their rain gear or you won't see them in rain gear until the Storm conditions are met. Its only when you can't fire the guns that the crew dons raincoats. I'm using the Bad Weather Guns mod, so it could be a hurricane out there and my watch crew will still refuse to don their gear.
Stormconditions are in the SHIII/data/submarine/NSS_Uboat(U boat type) folder. In each type's folder look for the NSS_Uboat(U boat type).cfg Each sub has its own Stormcondition listed in these .cfgs
What can I say. I lost to many kills because of 7m/s winds
The sun is shining brightly, and there is white caps on the waves, but I can't fire my frigging guns.