Mojave Desert - Climate

Climate

The Mojave Desert receives less than 13 in (330 mm) of rain a year and is generally between 2,000 and 5,000 feet (610 and 1,500 m) in elevation. The Mojave Desert also contains the Mojave National Preserve; as well as the lowest and hottest place in North America: Death Valley at 300 feet below sea level; where the temperature often surpasses 120 °F (49 °C) in late July and early August. The Zion National Park in Utah, lies at the junction of the Mojave, the Great Basin Desert, and the Colorado Plateau. Despite its aridity, the Mojave (and particularly the Antelope Valley in its southwest) has long been a center of alfalfa production; fed by irrigation coming from groundwater and (in the 20th century) from the California Aqueduct.

The Mojave is a desert of temperature extremes and two distinct seasons. Winter months bring temperatures dipping to around 20 °F (−7 °C) on valley floors, and below 0 °F (−18 °C) at higher elevations. Storms moving from the Pacific Northwest can bring rain and in some places even snow. More often, the rain shadow created by the Sierra Nevada as well as mountain ranges within the desert such as the Spring Mountains, bring only clouds and wind. In longer periods between storm systems, winter temperatures in valleys can approach 80 °F (27 °C).

Spring weather continues to be influenced by Pacific storms, but rainfall is more widespread and occurs less frequently after April. By early June, it is rare for another Pacific storm to have a significant impact on the region's weather; and temperatures after the middle of May are normally above 90 °F (32 °C) and frequently above 100 °F (38 °C).

Summer weather is dominated by heat. Temperatures on valley floors can soar above 120 °F (49 °C) and above 130 °F (54 °C) at the lowest elevations. Low humidity, high temperatures, and low pressure, draw in moisture from the Gulf of Mexico creating thunderstorms across the desert southwest known as the North American monsoon. While the Mojave does not get nearly the amount of rainfall that the Sonoran desert to the south receives, monsoonal moisture will create thunderstorms as far west as California's Central Valley from mid-June through early September.

Autumn is generally pleasant, with one to two Pacific storm systems creating regional rain events. October is one of the driest and sunniest months in the Mojave; and temperatures usually remain between 70 °F (21 °C) and 90 °F (32 °C) on the valley floors.

After temperature, wind is the most significant weather phenomenon in the Mojave. Across the region windy days are common; and also common in areas near the transition between the Mojave and the California low valleys, including near Cajon Pass, Soledad Canyon and the Tehachapi areas. During the June Gloom, cooler air can be pushed out into the desert from Southern California. In Santa Ana wind events, hot air from the desert blows out into the Los Angeles basin and other coastal areas. Wind farms in these areas generate power from these winds.

The other major weather factor in the region is elevation. The highest peak within the Mojave is Charleston Peak at 11,918 feet (3,633 m); while the Badwater Basin in Death Valley is 282 feet (86 m) below sea level. Accordingly, temperature and precipitation ranges wildly in all seasons across the region.

The Mojave Desert has not historically supported a fire regime because of low fuel loads and connectivity. However, in the last few decades, invasive annual plants (e.g., Bromus spp., Schismus spp., Brassica spp.) have facilitated fire; which has significantly altered many areas of the desert. At higher elevations, fire regimes are regular but infrequent.