By the end of the 21st century, some parts of the world can expect as many as 30 more days a year without precipitation, according to a new study. Ongoing climate change caused by human influences will alter the nature of how rain and snow falls; areas that are prone to dry conditions will receive their precipitation in narrower windows of time. Computer model projections of future conditions indicate that regions such as the Amazon, Central America, Indonesia, and all Mediterranean climate regions around the world will likely see the greatest increase in the number of "dry days" per year, going without rain for as many as 30 days more every year. California, with its Mediterranean climate, is likely to have five to ten more dry days per year.

Source: Number of days without rain to dramatically increase in some world regions