Is the heater working at all Ruth? alter the control to see if it works on your feet, the snow would not effect it, if the motor is not working check out the hand book & look for the fuses.
I've sometimes had items not working if I've had too many bits on together, e.g. lights, blower, windscreen wipers, heater...... turn off and after a bit it reset.
It was working fine on full blast for 20 mins then I turned it off for a bit and then tried on again and nothing, no air at all on feet, windscreen or wherever. Thought I must have left it on too long on hot because it's so snowy here.
Bit of advise Ruth, get this sorted ASAP if your cold within the car it can effect your reactions! think I'm joking? been there. Re/ get someone to check the fuse.
How old is the car Ruth? If it's a few years old then the wiring can start to deteriorate. Contacts can also become tarnished or corroded and need cleaning. It might even be the blower motor having come the the end of it's days.
The heater system is quite simple and basic for any decent mechanic and they should identify the problem quickly. If the worst comes to the worst you will have to have a new motor fitted (or a second hand one), although it's almost certainly not that. It's probably something very simple though like a poor earth or bad wire. Best to get it looked at soon though.