Driest Place in the United States
Death Valley is widely regarded as the driest place in the United States. That claim comes from a century of weather observations.
But the most recent decade of rainfall measurements reveals that another location seriously rivals Death Valley's status as the country's least rainy spot.
Least Amount of Rain
Until lately, Furnace Creek at Death Valley National Park in the Mohave Desert of eastern California, had less rainfall than anywhere else in the United States. Between 1971 and 2000, Death Valley averaged 2.3 inches (59 millimetres) of rain a year. It is the only place over the 30 years where a US weather station recorded less than two-and-a-half inches of annual precipitation.
Earlier years in Death Valley were even drier. From 1911 to 1960, the yearly rainfall averaged just 1.6 inches (41 mm). During the driest period on record there, only 0.68 inches (17 mm) of rain came in 40 months, from March 1931 to June 1934.
But while Death Valley became rainier over the last century, other arid spots got drier. One place worth noting is the city of Calexico, which sits south of the Salton Sea in California, near the Mexican border.
During the first decade of the 21st century in Death Valley, rainfall averaged 2.2 inches (56 mm) a year, similar to the previous three decades. Meanwhile, the average annual rainfall at Calexico dropped from 2.9 inches (73 mm) during 1971 to 2000, to just 1.7 inches (43 mm) from 2000 to 2009. Compared with Death Valley recently, Calexico received one-half inch less rain a year.
Years With No Rain
Death Valley does lead the country in the number of years lacking rain. A year of complete drought is rare, even in the most arid parts of the United States. Death Valley has had three dry years.
Calexico has no calendar year on record without rainfall. While Calexico did have over 12 rainless months, from August 2001 to August 2002, the least amount of rain it's ever received from January to December is 0.22 inches in 2002.
Fewest Rainy Days
On another front, Calexico further challenges Death Valley for the title of Driest Place in the USA.
Since the 1960s, rain has landed less often in the Imperial and Coachella Valleys around the Salton Sea than it has in Death Valley. Towns and cities such as Calexico, Niland, El Centro and Brawley averaged just 11 or 12 days of rain a year, while Death Valley had 16 days.
More frequent rainfall is another symptom of the climate in Death Valley growing wetter. Prior to 1960, Death Valley had an annual average of just nine rainy days.
Driest Place of the Century
Furnace Creek in Death Valley received the lowest total precipitation in the US during the 1900s. But if current weather trends continue, it won't keep that distinction through the next century. For the 21st century, the country's driest location might just be Calexico.
Steven Roof and Charlie Callagan. 2003. The Climate of Death Valley, California. Bulletin of the American Meteorological Society. 84(12): 1725-1739.