Instead of a block heater, I would install an inline coolant heater - you can buy 1" to 1.5" at Fleet and Farm. Get a timer, have it turn on 2 hours before you intend to blow snow. I would also set your battery up with fixed jumper leads to allow a quick connect to a trickle battery charger and have this powered on the timer as well. You will be happy to have a fully charged battery when it is COLD outside.