it never rains but it pours
When something occurs it often does so to excess. For example, First Aunt Sue said she and Uncle Harry were coming for the weekend and then my sister and her children said they were coming tooit never rains but it pours. This expression may have come from either a book by Queen Anne's physician, John Arbuthnot, or an article by Jonathan Swift, both entitled It Cannot Rain But It Pours and both published in 1726.
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