Driest States in America

All of the ten driest states in America average no more than 20 inches (508 millimetres) of rain and snow annually, based on state-wide averages of precipitation. Nevada takes the lead as the least rainy state in the US, with only 9.5 inches (241 mm) of rain each year. The mountain states, including Wyoming and Montana, dominate the list of America's driest states year round.

The driest time of year for most of the arid states is winter, when many in the top ten average less than an inch of precipitation a month. Even drier is California during summer when the state's monthly rainfall totals just a quarter inch (6 mm).

The states with the lowest amount of precipitation changes, though, from season to season. In winter, North and South Dakota are the driest in the country, but for spring, Arizona and New Mexico see the least rain. In summer, California and Nevada take the lead, then for fall, Nevada and Wyoming top the list.

Some states which rank among the country's 10 wettest for some seasons are among the ten driest states at other times of the year. Washington goes from being the sixth driest state in summer to the fifth wettest state in winter.

State-wide averages of precipitation give just a general indication of climate because they hide variations in rainfall and snowfall within a state. Especially for states with topography that ranges from ocean beaches to lofty peaks, total precipitation can vary enormously from place to place. In Washington State, for example, precipitation ranges from 102 inches (2,591 mm) a year in Quillayute on the rainy west coast to less than 8 inches (203 mm) a year at places such as Quincy and Ephrata in the central region of the state.