In winter, many northern parts of North America are very cold and there is deep snow. By contrast, the southern US states and Mexico are warm and often sunny.

Many people who have retired buy recreational vehicles (RVs, mobile homes) and travel south before the cold weather sets in, and stay in RV parks for the whole winter. Here they meet up with friends year after year.

Because the areas they come from are snowy - white, and the 'fly' away from the north to the south like migrating birds, these retirees are known as 'snowbirds'.

Many southern states get more tourists in winter than in summer because of the snowbirds.