Cold enough so that the rates in New York City, unable to find other things to eat, started chewing the bark off trees in city parks.
It seems, impossibly enough, that it was so cold that the rats couldn’t find their normal sense of food. Maybe frozen garbage isn’t even slightly appitizing.
Instead, the rats ate the bark off trees . In many cases, they girdled the trees, eating the bark compltely around the tree. that kills the tree because sap can’t flow past the girdled ring.
here’s the entire story: http://www.livescience.com/45064-nyc-rats-eating-trees.html_