banana belt

US, informal

1. :  a warm region —usually used in an exaggerated or facetious way to refer a relatively warm area in a region known for its cold climate … our last days on the peninsula (the arm of Antarctica that polar scientists disdain as the “Banana Belt”) … — Kate Ford, Wall Street Journal, 12 June 1998 Anything south of here is considered Oregon's banana belt—temperatures run higher than elsewhere on the Oregon coast. — Jacques Von Lunen, Oregonian, 2 June 2009