deepsruns

My car 2.5 TL 96 model does not blow hot air inside the car when the outside temperature is less than -20 deg C. I never use to have this problem before. Even in -40 deg C it use to heat the air pretty well. Now, I leave it running idle and the air becomes hot when the car is stationary in the parking lot but when I hit the road, the mercury dips and cold air starts coming out of the ducts and it remains that way while I am driiving. Can anybody tell why this is happening please?