Colder than a witch's heart

Here's a photo taken at Niagara Falls many decades ago. My better half, Linda, sent me this as part of an email which asks the question: "Who says there is no global warming?" Apparently, in 1911, Niagara Falls completely frozen over and people actually walked along the upper edge of the icy precipice. Colder than a witch's heart is how my granfather, Sid Thomas, would describe wintery scenes like the one above.
BtheB