Somebody says that it is raining cats and dogs. We know it means it is raining heavily. Here you can know why people say like this.
There are many large rats (老鼠) in a country. People need cats. But there are many mountains in the country. It's hard for a plane to land. So the cats come down by parachute (降落伞). In another country, the people need dogs to help people to find the people in the snow. Where can they get them? You can guess. The dogs come down by parachute. Both cats and dogs are coming down by parachute, just like the raindrops coming from the sky. So there is the saying "It is raining cats and dogs".
These cats and dogs help the people. And the people often say it rains cats and dogs. This kind of old saying is very interesting.
