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Summer Monsoon – It Begins

If you’re not familiar with the Sonoran Desert “summer”, it’s extraordinarily different from what we experience most of the year. While it’s true that it gets hot in the areas around Phoenix and Scottsdale in June-September, the low humidity makes it bearable. While it can get into the 90° or higher temperature range on the East Coast as well as the Sun Belt from Texas over to the Carolinas, the humidity can climb  to 80% or higher. That combination is about as bad as it gets. I was born-and-raised in the Carolinas, so I know that experience all too well.

On the other hand, we here in the Sonoran Desert experience temperatures in the 60’s-80’s for most of the year, with humidity levels in the single digits to low teens. It’s not unusual to see humidity at 5% in the hot dry months of the fall.

But (and this is a big but for us here), we have a phenomenon called the monsoon . The monsoon runs from mid-June through the early fall. Because of prevailing weather patterns, higher humidity from Mexico slides north into Arizona blending with our 107°-110° temperature days. This moist air then clashes with the significantly cooler air coming down from The Mogollon Rim. Rim Country is usually 30 degrees cooler than Scottsdale because the elevation is 6,000-7,000 feet above sea level. When hot, humid air smashes into cooler air, usually in and around the Phoenix area, monstrous thunderstorms fire up quickly. I’ve seen a sky with no clouds one minute evolve just one hour later into severe storm clouds exploding to tops of 15,000 feet or more. It’s in those rapidly rising funnels of heat and humidity in which severe monsoon storms are born, creating incredible lightning displays with thousands of lightning strikes hitting the ground during a typical storm. We’ll see high winds of 50-60 mph, blowing desert sand and dust, and dangerous driving conditions. We even have a law in our state called the Stupid Driver Law that recoups the cost of sending out emergency first-responders who extract drivers from vehicles who “stupid” enough to cross desert washes running up to 3′-5′ of water. Invariably, they get stuck and their cars simply float down the wash…even Hummers and F-350 pick-ups. Sometimes, they even drown.

These monsoon rains are eagerly awaited by us Sonoran Desert denizens because we need the water, and the rain also helps break some of the heat. But, it also adds enormous humidity to the air (by our standards at least), and that’s where it can get very uncomfortable. I believe I saw a statistic somewhere that the Sonoran Desert has 330 days or more of sunshine, and 80% of our normal annual rainfall of under 10″ comes during this 6-8 week monsoon period.

With that very first drenching monsoon storm, the local television stations will roll out their remote broadcasting trucks and beat reporters to show our desert washes running, parking lots ankle deep in water and accidents on the major freeways as oil/tire rubber on the highway becoming super slick due to the rain. In fact, these storms are what some locally call “Breaking News.” I guess you’d have to live here to really appreciate how people react to that very first monsoon storm each year.