What weather other than cold is it hard to keep a house warm in?

The larger the difference between inside and outside, the faster the heat loss from inside to outside. It is a RATE problem and has nothing to do with the subjective Words COLD and WARM. The key Word is the DIFFERENCE is proportional to RATE of heat transfer. The greater the difference, the faster the rate of heat transfer from the warm area to the cold area. Weather has nothing to do with the rate of transfer other than determining the difference between inside and outside. Windy weather will increase the rate of transfer by introducing turbulence at the wall surfaces which increases the rate of heat transfer because of the motion of the air near the surface. In weather circles, this is called "wind chill" which only means something where people and skin are concerned in connection with moving air surrounding your bare skin. However, it IS a measure of turbulence introduced cooling of ANY object by a surrounding, moving fluid such as air or water. Wind chill also takes into account humidity, and again, applies only to bare skin. The humidity determines the evaporative cooling of water in your skin as you sweat. You may not be aware, but you sweat all he time. You lose about 1 quart of water through your skin every day. The water evaporating is a cooling effect whether you feel wet or not. The greater the wind speed, the more cooling effect of the evaporation of water from the surface of your skin. The greater the RATE of heat transfer from inside to outside, the more heat input is needed inside to maintain a constant internal temperature. Heat flows exactly like water in seeking its own level.