Changing Rainfall Patterns

Rainfall is 50% higher now than in the past. Yearly precipitation consistently averaged about 1.6 inches of rain for the first 60 years of record keeping. The last 30 years has seen an average increase, averaging 2.5 inches of rain a year.

Longest Summers

The greatest number of consecutive days with a maximum temperature of 100° For above was 154 days in the summer of 2001. The summer of 1996 had 40 days over 120° F, and 105 days over 110° F. The summer of 1917 had 43 consecutive days with a high temperature of 120° For above.

The Highest Ground Temperatures

The highest ground temperature recorded was 201 ° Fat Furnace Creek on July 15, 1972. The maximum air temperature was 128° F. Ground temperature on the valley floor is about 40% higher than the surrounding air temperature. Although many factors have created a desert in the southwest, Death Valley’s unique geographic features cause desert conditions to become extreme.

Why So Dry?

Winter storms moving inland from the Pacific Ocean must pass over mountain ranges to continue east. As the clouds rise up they cool and the moisture condenses to fall as rain or snow on the western side of the ranges. By the time the clouds reach the mountain’s east side they no longer have as much available moisture, creating a dry “rainshadow”. Four major mountain ranges lie between Death Valley and the ocean, each one adding to an increasingly drier rainshadow effect.

Why So Hot?

The depth and shape of Death Valley influence its summer temperatures. The valley is a long, narrow basin 282 feet below sea level, yet is walled by high, steep mountain ranges. The clear, dry air and sparse plant cover allow sunlight to heat the desert surface. Heat radiates back from the rocks and soil, then becomes trapped in the valley’s depths. Summer nights provide little relief as overnight lows may only dip into the 85° to 95° F range. Heated air rises, yet it is trapped by the high valley walls, is cooled and recycled back down to the valley floor. These pockets of descending air are only slightly cooler than the surrounding hot air. As they descend, they are compressed and heated even more by the low elevation air pressure. These moving masses of super heated air blow through the valley creating extreme high temperatures.