 In weather maps, a band of clear air called the Föhn gap, which is over the downwind of the Blue Mountains region, can be seen between the wall and arched cloud cover – The gap is the region with clear weather, dry gusty winds and higher temperatures than those of the mountains.In the cool season, Föhn-like winds can be particularly damaging to homes and would affect flights, in addition to being uncomfortable, as the wind chill factor would usually make the temperatures feel cooler than what they are.These winds, which average between to , are generally brought on by a large polar air mass from the southwest and a deep low pressure system, typically in late winter and early spring.