When it’s raining heavily and the weather is particularly unpleasant, it is known as hondenweer [ˈɦɔn.də(n)ˌʋeːr] (“dog weather”) in Dutch, as you would only go out in it if you had to walk your dog.
This is a phrase I learnt last week from a Dutch friend. According to Wiktionary it means “particularly bad or rough weather, the kind of weather when it is raining cats and dogs”.
The equivalent in French is temps de chien [tɑ̃ də ʃjɛ̃] (“dog weather”), which refers to filthy, dreadful or awful weather [source].
If the weather is even worse, you might say that it’s weer om geen hond door te sturen (“weather through which not to send any dog”) [source]. There is an equivalent in English: I wouldn’t send a dog out in this.
Are there any interesting dog-related expressions in other languages?