If there's acid rain, is there such thing as acid snow?
As explained by user voltaic at reddit:


  Yes, there is, and it can be more of a problem than acid rain.
  
  For one, when snow is falling it spends more time travelling through
  the atmosphere before hitting the ground than rain. As a result of
  this, it has more time to collect pollutants, and can become more
  acidic than typical acid rain for the same region. There's additional
  factors that complicate this however, such as the solubility of the
  pollutant, the temperature and the water content of the snow, etc.
  (e.g. warmer snow which is more "wet" is going to dissolve more than
  cooler, drier snow.)
  
  Once the snow hits the ground, the dissolved pollutants are going to
  stay in solution, or trapped within the crystalline structure of the
  snow until it melts. Because of this, snow can pile up and then thaw,
  releasing all the pollutants and acidic water in a relatively short
  amount of time. This can have fairly substantial effects on the
  environment.
  
  You can read a bit more about this here:
  
  
  http://www.elmhurst.edu/~chm/vchembook/191acidsnow.html
  http://dwb4.unl.edu/Chem/CHEM869V/CHEM869VLinks/www.qesn.meq.gouv.qc.ca/cc/acidrain/info6.htm
  


Acid snow is also mentioned in passing on the acid rain wikipedia page.

The "fairly substantial effects on the environment", as described by the links above, largely involve a large release of acid during the spring thaw, which effectively releases all of the acid built up over the winter in a relatively short period. This can result in lowered pH in waterways, which can affect fish, amphibians and crustaceans.