title_body: Cause of seasonal difference in beer production
upvoted_answer: One thing you should take into consideration is that this chart certainly represents macro breweries production, once they still have the vast majority of the market-share, as opposite to craft breweries. So, we are talking here mainly about light lagers, known to be consumed as a refreshing beverage.
  
  So, to me, it's pretty clear that the production increases as the weather warms up, peaking at the summer, and then falls down again towards chiller seasons. Considering distribution and other delaying factors, the peak at June would match the peak consumption at mid-July through mid-August.
  
  PS: I don't live in USA, and this is merely a theory I came up with, but which seems feasible to me.