I have a 2004 WRX wagon and I was recently out in the snow with it, I noticed that there was a lot of what appeared to be steam coming from the engine bay and I pulled over to investigate. What I saw was the entire front of my car caked in snow (every orifice bellow the headlights). I removed the excess snow and saw that there were a few drips of green coolant in the snow and my coolant reservoir was practically overflowing. I keep it exactly on the full line. At the end of the ride I noticed my Check Engine light on. The next day I hooked my AP up and read it. PO117 Engine Coolant Temperature Circut Low Input. I also monitored the temp as it warmed up, and then I took it for a quick spin to see if the problem had resolved itself. I stayed in 1st and 2nd around the parking lot and after about a 5 min ride the temp was just starting to hit the upper middle temp line. A little above 200 degrees. So I turned it off and figured I'd ask about it. Please help I have to drive 200 miles home in less than a week. Thanks!
I would check the lower coolant hose to make sure you didnt get alot of snow in there and it pushed the hose off a little bit. Another cheap thing to do is it wouldnt hurt to throw a new thermostat in there. Check the coolant overflow tank and make sure it didnt crack.