When it rains, it pours
Actually, that refers to Morton Salt which has an anti-caking additive to keep the salt crystals separate in humid weather.
In 1914, the famous Morton Salt Umbrella Girl and slogan, "When It Rains It Pours®" first appear on the blue package of table salt and in a series of Good Housekeeping magazine advertisements. The slogan is adapted from an old proverb, “It never rains but it pours.”