1 change in the blink of an eye 瞬息万变
The weather change in the blink of an eye. 天气瞬息万变。
2 become cloudy and overcast 变阴天
It's common to go out on a sunny day and for the weather to become cloudy and overcast, then to have a downpour, then to become sunny again. 出门时是阳光明媚，之后就多云转阴，再后来大雨滂沱，最后又艳阳高照。这些都是普遍的现象。
3 four seasons in a day 天气时常迅速变化
The weather in my hometown is very changeable. One minute it's bright and sunny , the next it's cloudy and overcast. It's like four seasons in a day sometimes. 我的家乡天气反复无常。前一分钟还是阳光明媚的，下一分钟开始多云转阴了。有时候一天中能程序按四季。
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