my Steam sales have been terrible in last few days and it's incredible how I'm already in "panic mode" (not really justified since for example I had several itchio sales at same time :D). Indie psychology is hard!
for me there are no specific periods, all depends if I released a game in the past few months or not. Last year for example in the same period of August had made x4 the amount since I had released my RPG in May :)