Although I would defend Gothenburg against all kinds of accusations I can't really deny that the weather during the autumn and winter is crap. It's raining, it's windy, it's cold and everything is crap. Sometimes it does snow, but that isn't very often, and soon enough it gets back to raining again...
So make sure to visit Gothenburg in the spring (preferably from the end of April) or summer (until the end of September nowadays). Then the weather most of the time is great, warm enough to go without a jacket/just in t-shirt and not so windy either.
If you are in Göteborg by car during wintertimes be careful while driving around. It's not uncommon to have snow. It can be very slippery and most Swedish cars have 4 wheel drive or winter tires. So be prepared.