Monsoon season in the Southwest (July–September) produces sudden, intense thunderstorms with flash flooding in low-lying areas. Drivers attempt to cross flooded washes and end up stranded.
Flash floods are the deadliest weather phenomenon in the Southwest. Vehicles that look like they can cross often can't — water depth is misleading and the flow rate is much higher than it appears.
Stupid Motorist Laws (Arizona) allow agencies to charge motorists for the cost of rescue if they drive past 'road closed' barriers into floods. Costs can exceed $1,000.
If your vehicle is caught in floodwater: abandon it immediately if water is still rising. Cars float in less water than people expect. Get to higher ground.
Post-flood vehicle recovery is its own specialty — water-damaged vehicles often need full mechanical inspection. Don't restart a flood-damaged engine until it's been inspected.