Why can a desert have heavy rainstorms despite receiving little rain overall?

Deserts are defined by a chronic shortage of moisture, but they can still experience intense, short-lived rainstorms. These heavy downpours occur because desert rainfall is typically driven by local convectional cells rather than widespread weather systems.

When these localized storms occur, they can release a significant portion of a region's total annual precipitation in a very short period—sometimes within minutes or a single month. Because deserts often feature steep slopes, rocky surfaces, or hardpan soils that are not easily permeable, the ground cannot absorb this sudden influx of water quickly. This leads to rapid runoff, which can trigger a flash flood. These events are often brief, with water levels rising and falling within hours, leaving the environment arid once again.123