When the Desert Finally Gets Rain

HER Said (Cathy):If you’ve lived in Arizona, Nevada, or any desert city, you know we treat rain like a long-lost friend. We even have a name for our big dust storms, a “Haboob”. When the monsoon hits and rain mixes with desert dust, it’s dramatic, unpredictable, and always photo worthy. We grab our phones to film it, forget how to drive in it, and often overlook the one thing that actually connects us to the road… our tires. As a New York transplant, I quickly learned that driving in desert rain is a whole different experience not to mention a Haboob.

HE Said (Michael): From an engineering perspective, rain on desert roads creates one of the most dangerous driving environments in North America, especially in Arizona’s summer monsoons. After long dry stretches, oil, rubber dust, and debris collect on the pavement. The first rainfall lifts these contaminants to the surface, and traction can drop by as much as 50 percent, a fact most drivers do not realize until it is too late. On an oily wet surface, hydrodynamic effects also begin earlier because the oil water mixture forms a more uniform and less permeable film. That means hydroplaning can start at lower water depths and lower speeds than with water alone. In short it goes from slippery to really really slippery.

Together, we have assembled the five things every desert driver should know about tire safety before the next storm hits.

(1) The First Ten Minutes Matter Most

HER Said: That first light rain is the trickiest. Desert highways have not seen water in weeks or months, so the mix of oil and sand makes them far slicker than they look. Slow down and give yourself extra space. Even experienced drivers can lose control in those early minutes.

HE Said: The initial rainfall lifts oil molecules and fine particulates to the road surface. This reduces the friction coefficient between tire rubber and asphalt, sometimes by up to 50%. Once heavier rain flushes the surface, traction improves, but those first ten minutes are statistically the highest risk period for spinouts.

(2) Tread Depth: Where Safety Starts

HER Said: You do not need to be a mechanic to check your tread. Take a quarter, insert it upside down into the groove, and if you can see the top of Washington’s head, it is time for new tires.

HE Said: Less tire tread depth means higher hydroplaning risk. Anything below 4/32 of an inch (i.e 1/8” for the normal folks) puts you in the danger zone. At highway speeds, each tire must pump nearly a gallon of water per second to maintain grip. If tread channels cannot displace that volume, water builds up beneath the tire, turning it into a water ski. At that point, steering and braking effectiveness temporarily vanish.

Howard Fleischmann – Co-Owner Ed Whitehead Tire Pros “In climates like Arizona, heat accelerates tire aging. Drivers should inspect tread depth and sidewalls twice a year, not just before long trips.”

(3) Tire Pressure Drops When Temperatures Fall

HER Said: Monsoon storms can drop the temperature 20 degrees in an hour. That also drops your tire pressure, but most people don’t notice until the dashboard light comes on. Check your tire pressure monthly, not just when it rains.

HE Said: Here’s the physics behind why your low tire warning might trigger in a rainstorm. For every 10°F drop in temperature, tire pressure falls by about 1 PSI. When tires are underinflated, the contact patch widens, rolling resistance increases, and the risk of hydroplaning goes up. Keeping tires at the manufacturer’s recommended pressure ensures the tread’s water channels can do their job.

(4) Hydroplaning: The Hidden Danger

HER Said: If you feel the car start to glide, do not panic. Ease off the gas, keep your steering steady, and avoid sudden braking. You’re not in Seattle where rain is a staple, you are in the desert where rain is sudden and dangerous. FYI: Aquaplaning is another term for Hydroplaning.

HE Said: Hydroplaning can occur at speeds as low as 35 miles per hour with just one tenth of an inch of standing water. When tread channels overload, a wedge of water forms beneath the tire, lifting it off the road. Steering control drops to near zero until traction returns. The goal is to slow down without losing control. Ease off the throttle, brake gently, and avoid sharp steering inputs. Once you feel the tires reconnect with the road, you can brake more firmly if needed. During summer rainstorms, you get a double effect: cooler ambient air plus the convective and evaporative cooling of rain on the tires. The air inside can drop 40–70°F, which equals a 4–7 PSI loss, enough to make the difference between holding traction and hydroplaning.

Safety Stat: 12 percent of accidents are weather related and the vast majority are during rain and mist. In other words, bad weather equates to 750,000 crashes/yr with 270,000 injuries and 3,800 deaths.

(5) Replace Tires Before the Tow Truck Comes Calling

HER Said: Desert heat does not just fade paint and burn skin; it cooks your tires. Even if the tread looks fine, UV rays and heat can crack sidewalls. Do not wait for a blowout to ruin your day. Arizona holds the record for the highest recorded temperature in the United States, with a scorching 128 degrees in 1994. I remember it well, so do my tires.

HE Said: Rubber in the southern belt breaks more quickly and accelerates tire aging for four reasons:

• Heat: Pavement at 150 to 170 degrees accelerates rubber aging 2x-3x faster than normal.
• UV Radiation: Sunlight makes rubber brittle, leading to cracking and loss of elasticity.
• Ozone: High levels in sunny regions attack rubber at the molecular level, causing ozone cracking.
• Dry Air: The lack of humidity in desert climates hardens rubber faster than in northern climates.

Together, these factors mean tires, engine mounts, hoses, seals, and even wiper blades wear out in the desert at about twice as fast as in cooler regions.

HER Said: We all drive on the same roads, but some of us listen to intuition and others to equations. When both come together, we are safer and smarter. Because I have test driven more than 700 vehicles, I make sure that when I insert the quarter, I see all of Washington’s head.

HE Said: You always have a way with words Cathy, but physics rule the road! The data makes it clear that preparation matters. Check tread depth, tire pressure, and alignment before the storm so you do not need the tow truck after the storm!

- Cathy Droz is the founder of HER Certified  

- Michael Petersen is the founder of Raise a Hood