alt Hacker NewsThis is a concern of mine, and my attics (3 of them due to the way the house is built) are pretty inconvenient to check, so I put some battery-powered temp/humidity sensors in them.
Haven't gotten around to setting up any alerting thresholds though... I'm not actually entirely sure what temp/humidity thresholds would actually be useful.
Maybe you could put a camera up there to check for snow. Not sure how you'd power it if it was wireless though, not a lot of solar energy in an attic.