Make sure the air exhaust vent pipe is not restricted and the outdoor vent flap will open when the dryer is operating. Once a year, or more often if you notice that it is taking longer than normal for your clothes to dry, clean lint out of the vent pipe or have a dryer lint removal service do it for you. Blockage in dryer exhaust vents can also occur from the nests of birds or other animals.
Clothes dryers should be vented directly to the outside. Serious hazards occur when dryer vents do not exhaust directly to the outside. CLEAR AWAY THE SNOW!