Right country, wrong month. Crayfish premier, 5pm, first Wednesday in August. Partying usually starts any day that week when you don't have to go to work next day. Menu: Vodka, crayfish boiled with loads of dill, cheese pie (must be Swedish cheese), beer, bread, butter - in that order. It's a very messy affair and bibs and silly hats are obligatory.
I think I found a suitable photo: