We learned that: If no cup is available for washing one's hands, one can immerse them into a river or into snow, if there's enough snow on the ground to fill a Mikve. (About 500 litres/130 gallons of water.)

This applies to washing three times after arising as well as washing before eating bread.

Source Kitzur Shulchan Aruch 2:6, 40:7

Somebody wanted to know if one could tovel dishes in snow. Any sources for an answer?