You've visited Borås? Anyway, we have this rule called the V2 which demands that the verb must go in second place in most sentences (in main clauses that are not questions). So it must be Det regnar alltid i Sverige.
It's cool that you've even heard of the place at all. It's a town (wikipedia calls it 'city', but I think that's a bit too generous) in Western Sweden that has the reputation of being the rainiest place in Sweden. It has also been voted 'most boring town/city' :D