Death Valley in summer:
While working in Death Valley, we found that nearly all visitors in summer were from Europe. Most said that they came to the U.S. when they had their vacation time which typically fell in the summer. They all had guide books and all the guide books list "must see" places which include Yosemite, Grand Canyon and Death Valley. Makes for a good trip with DV between the other two. Few had any concept of what 50 degrees C felt like before visiting. Of course, few Americans have any concept of what 125+ degrees F feels like. I recall a German couple who traveled the back road (dirt) from Big Pine to north Death Valley and when they arrived at the Grapevine Ranger Station came in and told me that it was so hot and so deserted that they "were lucky to be alive."
Lucky indeed. In August of 1996, four Germans took off for the Valley from Las Vegas...and disappeared. Their car was found in October of that year. The Germans were never found...except, I suspect, by the coyotes and vultures. As I remember, they took the southern CA-78 route into the Valley -- 80 miles with no services or much of any thing else.
Death Valley is a huge basin set in the midst of the Great Basin Desert of the southwestern USA. Oriented north-south, it is about 120 miles (200 km) long, and 10-20 miles (15-30 km.) wide. The basin was created by downfaulting of the floor of the basin to a point over 3000 feet below the surrounding deserts. The downfaulting continues to the present day. Together with a similar area to the south, the Salton Sink, and to the north, the Carson Sink, Death Valley is believed by some geologists to represent the rifting of the North American continent and the development of new ocean extending from the Gulf of California northward to a line about 50 miles (83 km.) south of the northern border of California.
The passes into the Valley, which is bounded by mountain ranges, must ascend 1000-1500 feet (300 to 450 m.) and then descend some 1200-5000 feet (360 to 1500 m.) into the Valley. Leaving the Valley means a 4000-5000 foot ascent, which in the summer is through hellish heat.
Because the Valley is a active fault basin or rift zone and not a water-cut true valley, the topography takes on a nature unfamiliar to those from less violent geology and wetter climates. The canyons or valleys that enter the basin are narrowest at their mouths, so that a narrow canyon may drain a wide area above and tributary to it...a shape is rather like a wineglass with the canyon as the stem. Wineglass drainage can be seen most clearly in Titus, Golden, Mosaic, and Grotto Canyons. The canyons open onto great fans of silt, sand, gravel and boulders that spread below the mouths of the canyons and form aprons around the base of the mountain ranges.
Summer temperatures will range from 110 to 130?F (43-53?C). The record at Badwater is 134?F (56?C)! The ground is even hotter: 50 to 70?F (28-39?F) higher than the air temperature. The record for ground temperature in Death Valley is 201?F (93.8?C)! The measurement was on natural ground. A black asphalt roadway would measure than materially higher than that.
At temperatures over body heat (99?F or 37?C), the breezes are no longer cooling. In fact, they are hot blasts that serve to overheat the body by moving freshly heated air against it like the blast of a furnace. Therefore, at those temperatures, you cool yourself by staying out of the "breeze".
Death Valley has an annual rainfall of around 1-1/2 inches (3.81 cm.). In the summer there is no standing water, except for a few small springs. As a result the relative humidity ranges between 10% and 0%. The mountains and surrounding the Valley do experience tropical thunderstorms during the monsoon season of August and September. [Yes, the American Southwest does have a monsoon, in the form of extremely violent thunderstorms ranging up from the Gulf of California and the Sea of Cortez.] These thunderstorms can dump huge amounts of water on the drainage of a wineglass valley, the runoff piles up in the narrow canyon and shoots out into the dry washes in the fan in flash floods. The floods are violent enough to carry the boulders that you see on the outwash fans at the foot of the mountains.
