The Laguna Mountains block out incoming coastal moisture. Without water, the areas is a dry, barren desert. Located on the eastern edge of the county, the Colorado Rivers supplies irrigation water for a half million acres of farmland. Saline drainage water flows north to the Salton Sea, a body of water more saline than the ocean. Mexico is the southern border of the county.
Soils consist of very fertile, alluvial deposits from the Colorado River flood plain.
These soils may be as deep as a mile in places. Nitrogen and phosphorus fertilizers are needed for vegetable production. Imperial Valley has a well-known reputation for midwinter salad vegetables. Shipments of crisphead lettuce, leaf lettuce, cauliflower, broccoli, and cabbage start in December and continue until March. Asparagus is in-season January, February and March.