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July-August 2010

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Retrospect: July 10, 1913: Highest Temperature Ever Recorded in North America

“Hottest, Driest, Lowest—A Land of Extremes.” That's how the National Park Service describes Death Valley National Park, a vast area of more than 5,000 square miles in California's Mojave Desert. Surrounded by mountain ranges with peaks that rise up as high as 11,000 feet above sea level, Death Valley contains the lowest point in North America: Badwater Basin, whose elevation sinks to a staggering 282 feet below sea level. It is here that sparse desert land (which only sees an average of about two inches of rain per year) is heated by the sun and, in turn, heats the air above it to extreme levels. The process is reinforced by other geographic and climatic factors, including the fact that Death Valley lies on the lee side of several mountain ranges, including the Sierra Nevada. This places it in an area known as a “rain shadow,” where once-cool, moisture-laden air from the Pacific becomes increasingly dry and heated as it flows down-slope toward the valley floor in a process known as adiabatic warming.

Although weather observations at Death Valley date as far back as 1861, official recordkeeping began in 1911, when the U.S. Weather Bureau established a cooperative observing station at Greenland Ranch, now known as Furnace Creek Ranch, about 14 miles north of Badwater Basin and at an elevation of 178 feet below sea level. The station, set up according to an arrangement made between the Weather Bureau and the Pacific Coast Borax Co., was maintained by Oscar Denton, the caretaker for the ranch.

Just two years into its operation, Denton made climatological history when he recorded a daily maximum temperature of 134°F (56.7°C) on July 10, 1913. Never before had anyone recorded such a high temperature at an official weather station anywhere on the globe. In fact, the 134°F reading would remain the highest temperature on record for not only the United States and North America, but worldwide for nearly a decade, until a reading of 136°F was reported at El Azizia, Libya, on September 13, 1922.

Caption: U.S. Weather Bureau Daily Weather Map for 8:00 a.m. Eastern Time, July 10, 1913. It was on this day that the record highest temperature for North America (and, at the time the world) was recorded at Greenland Ranch, in Death Valley, California. On this map, Greenland Ranch lies just north of the 70°F isotherm—a clear indication that the larger synoptic scale conditions do not account for the harsh microclimate of Death Valley.

The record reading at Greenland Ranch occurred during a particularly hot spell from July 8–14, 1913, that was later described by George H. Willson of the Weather Bureau as “probably the most remarkable authentic record of high shade temperatures ever made.” During this period, the thermometer at the official Weather Bureau station registered a maximum temperature of at least 127°F each day and never fell below 85°F. Denton reportedly said of the record day, “It was so hot that swallows in full flight fell to the earth dead. When I went out to read the thermometer with a wet Turkish towel on my head, it was dry before I returned.”

Despite such harsh conditions, San Francisco District Forecaster Alexander McAdie published a report on the relative humidity of Death Valley in the June 1913 issue of Monthly Weather Review (which, due to the lag in publishing time, actually included temperature data from early July) in which he claimed “that the dreaded terrors of heat and dryness in Death Valley have been somewhat exaggerated; and that it is quite possible if proper care be taken in the matter of supplies and provision for physical comfort, to live and work in this section.”

Soon after reports of the record temperature began circulating, questions arose as to its validity. Apparently, when Denton sent his monthly observer form into the Weather Bureau, he attached a note saying that he doubted if the record was sufficiently high, since the official Weather Bureau thermometer only went as high as 135°F—one degree above the record—and since other thermometers at the ranch showed a much higher temperature that day.

The July 1915 issue of Monthly Weather Review included the following brief statement made by Fred Corkhill, the Borax Company's superintendant at the Greenland Ranch, which corroborated Denton's observation:

Regarding the temperature of 134°F, which was recorded [at the Greenland Ranch] on July 10, 1913, I will state that this record should be considered correct. I remember the day very distinctly, as a man by the name of Busch perished in the valley north of the ranch that day on account of the heat. I do not know in which direction the wind was blowing on that day, but it was blowing very hard from either the north or the south. The chauffeur who was with Mr. Busch at the time he perished also very nearly lost his life. I saw him a few days later and he said that a terrific wind prevailed in the valley on that day.

In 1949, climatologist Arnold Court published a detailed review of Death Valley's extreme temperatures, including the 1913 record of 134°F, in an article titled, “How Hot Is Death Valley?” which appeared in the journal Geographical Review. In examining the surrounding environment of the weather station, the equipment and procedures used for taking the observation, the weather conditions on that day, and temperature frequencies at the station over the period of 1911–1947, Court determined that a temperature of 134°F has a probability of occurring only once in 650 years. He also noted that the unusually high temperature may have been the result of a sandstorm that occurred that day, which could have caused superheated sand, dust, or other particles to come in contact with the thermometer (which was inside a regulation instrument shelter with louvered sides) and concluded that “constantly increasing accuracy in weather observations and higher standards of instrument exposure make it seem probable that no future official observation will exceed the present high temperature record for North America now held by Death Valley.”

Caption: U.S. Weather Bureau instrument shelter at Greenland Ranch, Death Valley, in 1922.

Court's theory of superheated sand coming into contact with the thermometer and causing it to register a temperature higher than the surrounding air may be valid. The National Park Service reports that the highest ground temperature recorded in Death Valley was 201°F at Furnace Creek on July 15, 1972, a day when the maximum air temperature reached 128°F.

Despite any uncertainties, the temperature reading of 134°F at Greenland Ranch remains the accepted record for the state of California, the United States, North America, and the Western Hemisphere. A recent study of the climate of Death Valley, which includes a discussion of the record temperature, was published by Steven Roof and Charlie Callagan in the December 2003 issue of the Bulletin of the American Meteorological Society.

Contributing Editor SEAN POTTER is a New York-based Certified Consulting Meteorologist (CCM) and science writer with an interest in weather history.

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