以下是几条含有天气类单词的短语,你能猜出划线部分的含义吗?

以下是几条含有天气类单词的短语,你能猜出划线部分的含义吗?
1.I'm under the weather today.Don't play jokes on me.
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2.Bad luck!It's raining cats and dogs.We have to stay at home.
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3.It never rains,it pours.Our shop had only one visitor this
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morning.But at aound 4pm we had more than twenty and a group of tourists came at the same time.