title_body: Brewing: Which temperature should I ferment ale beer at?
upvoted_answer: Short answer: 17-20C (62-68F) is good for ales.
  
  The temperature of fermentation is exceedingly important for the final beer.  Too low (&lt; 15C) can cause the ale yeast to go dormant, stalling the process.  While a high temperature (> 25C) can cause a rapid ferment, where the yeast creates excess esters and fusel alcohols.
  
  Yeast also generate their own warmth during fermentation.  A commonly cited value is that the ferment is around 3C above ambient temperatures.
  
  There are exceptions to this of course.  Some beers ("Saison" for example) are fermented much warmer.