The area encompassing Twentynine Palms is the Morongo Basin and is classified as having an arid, upland desert climate. The summer months are characterized by high temperatures, low humidity and clear, sunny days. While the average annual temperature is 67 degrees, temperatures occasionally reach 120 degrees in the summer and drop to 15 degrees in winter. Average annual precipitation is about four inches, most of it occurring as rain from July to January. Some freezing rain and snow does occur during the winter at higher elevations.
The terrain consists of steeply sloped mountains with flat intervening valleys that are oriented northwest-southeast. Relief is moderate, with elevations ranging from 1,800 to 4,500 feet. most mountain segments have approximately 2,000 feet of relief from the valley edge to their summits. There are also several dune areas, lava flows, and dry lakes that collect water during brief periods of heavy rain.