• Sunrise at the Cholla Cactus Garden

    Joshua Tree

    National Park California

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  • Cottonwood Trails Closed

    Trail access remains closed to Cottonwood Spring Oasis, Lost Palms Oasis, and Mastodon Peak. More »

  • Pinto Basin Road Under Construction; Expect 30+ Minute Travel Delays

    Visitors should expect 30+ minute waits when heading north and sound bound on the Pinto Basin Road. Due to construction activity around Cottonwood Visitor Center, additional waits of 30 minutes may be in place when leaving the visitor center parking lot. More »

  • Deteriorating conditions of Black Rock Canyon Road

    The road leading to Black Rock campground has deep potholes, is deeply rutted, and can be difficult to negotiate, especially in large vehicles. Please drive with caution.

Deserts

Some sources define a desert as an area receiving no more than ten inches of precipitation annually. However, many areas receiving this amount of precipitation are not deserts. This definition is not complete. Both the timing and type of precipitation determine the environment established.

In a desert, rain isn’t evenly distributed throughout the year. Weather patterns often create short, violent downpours that produce flash floods. Much of the water runs off before it can soak into the soil. A lot of moisture is also lost to evaporation.

Many deserts lie in areas of high pressure systems where there is little cloud cover. At least 90 percent of the sun’s rays reaches Earth’s surface, producing seasonal hot temperatures. (For comparison, the surface of more humid lands, covered with more vegetation, receives only 40 percent of possible solar radiation.) The hot, dry air causes any available water to evaporate quickly.

When temperatures are extremely hot, rain can evaporate before it reaches Earth. The conditions producing high daytime temperatures reverse the process after sundown. Approximately 90 percent of the day’s accumulated heat radiates back toward the sky. (In moister climates only about 50 percent of this heat is lost.) These conditions produce the wide range of daily temperatures characteristic of deserts. This range is often 50 degrees or more.

The rapid heating and cooling of air create another characteristic of most deserts: strong winds. These winds, circulating air that is often hot and dry, increase the already high rate of evaporation. Evaporation in American deserts ranges from 70 to 160 inches per year.

A desert then is not so simply defined. Several characteristics: seasonal, high temperatures; low, sporadic rainfall; a high rate of evaporation; wide temperature ranges; and strong winds are part of the definition.

Did You Know?

Desert Queen Ranch branding iron

In the high desert country that was to become Joshua Tree National Park, rugged individuals tried their luck at cattle ranching, mining, and homesteading. William Keys and his family are particularly representative of the hard work and ingenuity it took to settle and prosper in the Mojave Desert. More...