1·Since cold air sinks, and these spots are shaded, they are usually much cooler than the surrounding area.
由于冷空气下沉，这些斑点被遮蔽，它们通常比周围的地区要冷得多。
2·It's a phenomenon that occurs anywhere you have a large lake that doesn't freeze and have cold air flowing over it, mostly in the Northern Hemisphere Like the great lakes in the United States.
这种现象发生在不结冰的大湖泊附近，这些湖通常被冷空气包围着，并且它们大多数坐落在北半球，就像美国的五大湖一样。
3·Cold air also has a drying effect, which can increase the risk of dehydration.
冷空气也有干燥的效应，会增加你脱水的危险。
4·Cold air can trigger chest pain or asthma attacks in some people.
冷空气可能会引发胸疼或者哮喘。
5·A layer of cold air remains near the ground as smoke and fumes pour into it.
当烟尘和微粒拜谢到空气中以后，有一层冷空气仍然在贴近地面。