The _expression first appeared in print in 1653 ("It shall raine . . . dogs and polecats").
In mythology, the cat is believed to have great influence on the weather.
Witches that rode on storms were said to take the form of cats.
The dog is a signal of wind, as it was an attendant of Odin, the storm king.
So cats symbolize heavy rain,and dogs symbolize strong gusts of wind.
Another possible origin of the _expression is that the drainage of medieval streets was so poor that cats and dogs
frequently drowned during a heavy downpour.
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