Huddled in doorways and tucked into underpasses, tens of thousands of Americans sleep on bedding made of cardboard, plastic tarp and thin fabrics that offer little protection from the cold, hard concrete beneath. On any given night, more than 13,000 people are homeless in Georgia alone. Some sleep in shelters, but almost 6,000 people do not. Hypothermia begins to set in at 50°F. On winter nights in Georgia — among America’s mildest states — temperatures often plummet to below 20°F. All over the country, the story is the same: Insufficient shelter space leaves people no other choice but to sleep outside, at the mercy of the elements.