What temperature does snow develop? Does it have to be below 33 degrees or freezing?

Yes it is 32 degrees.

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fcst/prcp/rs.rxml

No,

Snow can occur at the earths surface at temperatures up to 45 degrees. It all depends on the amount of moisture and the thickness of the freezing level above the earths surface... If the freezing level is just above the earths surface, the snow doesn't have time to melt, so it will fall a temperatures above freezing. :)

It won't necessarily stick though!