因为冷却空气会去掉水分,而加热空气不会改变实际的湿度。当空气变冷,它不能持有尽可能多的水蒸气(低饱和蒸汽压)。当空气变暖,它可以"持有"更多的水蒸气(更高的饱和蒸汽压)。——所以当空气冷却到30 s°F,设置限制的水分(露点不能高于30年代)。然后加热到70年代,这是缺少水分。——而当夏天气团加热到80年代,90年代,超越外,气团并不改变水分(事先极限是什么…不同的位置/气团,但相当潮湿的地区如美国东部和欧洲,这是相当通常在50年代/ 60年代和70年代)。当你冷静下来时,它仍然有原来的天花板。所以72°F在夏天会有露水点在像60年代和非常高=更高的相对湿度…但在冬天,72°F将有露水点在像20多岁或30多岁或更低=低相对湿度)(露点是反映更多的* *温度最低的一天。 So if it's 30 °F outside in the daytime, but 10 °F at night... the 10 °F is the ceiling of the dew point of that air mass. Likewise, if it's 90 °F during the daytime, but 65 °F at night, the dew point is capped around 65 °F. But that's still quite moist compared to winter air masses) (Unlike a house heater, quick outdoor warmups are driven by warm fronts/warm air advection, which tend to bring in a different airmass, pulled in from more tropical regions, where the air also has also had plenty of time to evaporate moisture into it) (And air outdoors inevitably infiltrates/mixes indoors over time. So that colder, drier air will eventually come inside. You'll heat it, but it still doesn't have the moisture in it that the summertime air does. ... Plus even apart from that, with it quite cold outside and warm and moist inside, the windows and other boundaries will cause the air touching it inside to condense because the surfaces get cold. Conversation of mass suggests it'd generally reevapoprate when warmer unless you clean it up, but given most areas get cold regularly during the winter, the "puddle" would tend to be a pretty permanent feature if the air managed to be moist [try steaming some vegetables for a while, or running a humidifier, and you'll see this])