List of Arizona Hurricanes - Climatology

Climatology

Tropical cyclones are not common over Arizona, but on average, a tropical storm or a tropical depression enters the state approximately every five years. However, indirect flash floods caused by the remnants of tropical cyclones are more common, as they tend to occur about every two years.

Storms that approach the southwestern United States, and by extension Arizona, generally form closer to the Mexican shoreline than average, making them more likely to recurve northwards under the influence of an approaching trough. These troughs tend to extend farther to the south during the latter part of the Pacific hurricane season, in the period between late August and early October. These pronounced troughs thus produce a synoptic-scale flow that is conducive to steering hurricanes towards the southwestern United States.

The infusions of tropical moisture from Arizona-bound tropical cyclones can be a significant portion of the rainfall in the region. In years when hurricanes approach Arizona, eastern and northern portions of the state receive on average 6–8% of the monsoon-season precipitation from tropical systems and their remnants. This percentage rises towards the southwestern corner of the state, which can receive up to a quarter of its monsoon-season rainfall from tropical cyclones.