Is the dust dry....I keep my dust in a plastic bag in the garage...believe me it will take in moisture from the air. I know some folks pop the dust in the microwave for a minute or two..I've tried this with little success, I now put a tray of dust in the microwave but use the grill for abount 5 mins...this works for me...I did the other week when I smoked my last lot of bacon.
As for the outside temp being near zero, I've never found it a problem....for a cold smoke this will help. The reason any fire goes out is oxygen...I sit my box under the garage door, turn it so the bottom vent is facing the wind...and away she goes...
Ice.