Monsoon start/end: The Arizona portion of the North American Monsoon officially gets under way on June 15 and lasts until Sept. 30. That doesn’t mean we start magically seeing thunderstorms across our state. It’s a lot like the hurricane season in the Atlantic; it’s the time of year when hurricanes are most likely to occur. It's the same idea with this relatively new version of the monsoon; statistically, the chances for thunderstorms increase this time of year.
Monsoon arrival: In the Valley, the traditional arrival, or start, of the monsoon, is when dew points reach an average of 55 degrees or more for three straight days. Usually this occurs around July 7 in metro Phoenix.
Rainfall: In Phoenix, we get typically get 3 inches of rain or less during the summer thunderstorm season. And lately, it’s been dry. In eight of the past 10 years, we’ve had less- than-average summer rain. Much more rain is recorded in eastern and southeastern portions of Arizona.
Lightning becomes a major potential problem. Our cloud-to-ground lightning strikes statewide can top 500,000 per year and a large outbreak of storms around the Valley can result in literally tens of thousands of strikes in a single day. Besides the obvious threat to human health and structures, lightning starts numerous forest fires in Arizona each summer, especially early in the monsoon.
Flash flooding is also a major problem. Authorities are always telling us not to cross flooded washes in our cars or other vehicles. Yet every year, it seems, our first responders are put in harms way rescuing stranded vehicles and people.
Dust storms: Usually most of the dust storms we see are early in the season when the ground is very dry. Last year, 2011, was the “Year of the Dust Storm” in metro Phoenix. Dust storms reduce visibility to near zero in a matter of seconds. In recent years, we’ve had several fatal vehicle accidents blamed on dust storms.
For safety tips, check out the ADOT website. They, along with the National Weather Service, the Department of Public Safety and the Governor's Office of Highway Safety, have launched a special public-service campaign called "Pull Aside, Stay Alive." They want to kame sure you know exactly what to do if you're caught in a dust storm while on the road.
Forecast: We’re expecting a hotter-than-normal summer in Arizona in 2012 and about average rainfall. Most likely, the monsoon will “arrive” a little late in most locations. That being said, the monsoon circulation is notorious for developing rather quickly once the pattern unfolds, so we’ll keep a close eye on it in the 3TV Weather Department.