Plugs in cold climates

[NDblackstang]

Anybody had trouble with plug fouling using plugs one heat range cooler than stock in a brutally cold climate?

My plugs fouled this winter, beginnning a cascade of misfires in a very short time until the car was undriveable. Temperature here in ND has been below zero most days with some days as low as -20. My trips are short--could the Autolite HT-0 plugs be too cold for complete combustion on a cold soaked car under those conditions?