Amid subzero temperatures, here are the warmest beaches in the US ,if lying on the beach with a daiquiri in one hand and a good book in another has moved way up on your priority list this frigid winter, and you want to get warm — really warm — without leaving the U.S., your best bets are south Florida, Southern California and Hawaii. Here’s our list of the warmest beaches in the U.S. from December through February.