Whether you’re new to Arizona or a native, you probably assume it’s one of the driest states in the nation—and you would be right. Arizona ranks in the bottom five states for average annual precipitation, but it also experiences a weather phenomenon called the monsoon, during which storms can dump more water than you would imagine. Here’s what you need to know to protect yourself and your home during the Arizona monsoon.
MONSOON
Typically experienced during the summer, Arizona monsoon storms bring increased humidity levels, wind and dust storms and periods of heavy rain.
Derived from the Arabic “mausim” meaning “season,” or “wind shift,” the word “monsoon” refers to a season by definition. Historically, the monsoon officially began when three consecutive dew points above 55 degrees were recorded. (Dew point is a measure of the amount of moisture in the air—usually below 40 in the dry desert.)
Beginning in 2008, the National Weather Service declared that the Arizona monsoon officially begins on June 15 whether there is a change in the dew point or not. The last official day of the monsoon is September 30. This change was made, at least in part, to allow the Weather Service the opportunity to consistently promote safety messages connected with the monsoon season.
MONSOON FACTS
- 32% of Arizona’s yearly rain totals come during the monsoon.
- Lightning will strike about 500,000 times during the monsoon.
- The most rain generated from an Arizona monsoon was 9.38 inches in 1984.
- The driest monsoon in Arizona was .35 inches in 1924.
- The temperature is usually around 105 degrees during monsoon season.
OTHER LOCAL WEATHER IN ARIZONA
Arizona is home to other unique weather patterns, such as microbursts, haboobs, and flash floods.
MICROBURST
Tornadoes are relatively uncommon in Arizona, but quick-hitting, damaging, and sometimes rotating winds with scattering debris can occur during monsoon. These are most likely microbursts.
HABOOB
In 1971, a group of scientists witnessed an Arizona dust storm so huge they proposed calling it a haboob, the term used for the infamous dust storms in Sudan. Haboob comes from the Arabic word habb, meaning “wind.”
A haboob is a wall of dust that is a result of a downburst where air is forced downward and pushed forward by the front of a thunderstorm cell, picking up dust as it travels across the terrain. The cells are so close to one another they merge in what appears to be a solid wall of dust. The walls can be up to 62 miles wide and more than a couple miles high.
FLASH FLOOD
Flash floods can be produced when slow-moving or multiple thunderstorms occur over the same area. The metro area has improved drainage systems over the past several years, but heavy rains don’t always drain quickly in the desert.
SAFETY TIPS
- If you’re driving and enter a dust storm or haboob, pull off the road as soon as possible and as far from travel lanes as you can. TURN OFF YOUR LIGHTS. Drivers with little or no visibility behind you may think you are still on the road and follow you.
- If you’re outside and see a dust storm or haboob coming, seek shelter immediately. If you are caught outside, protect your ears, nose, mouth, and eyes with any kind of clothing you may have.
- Avoid driving through big puddles or through washes when there’s water present—no matter how shallow it appears. Sounds silly, but every year people are stranded in their vehicles because they thought they could make it and they were wrong. As a result, Arizona has a statute affectionately called The Stupid Motorist Law. The gist of the law is that if government resources are used to rescue you from a flash flood in an area where you should have known you weren’t supposed to drive, you could be charged for the police, fire, helicopter, and other expenses associated with the rescue.
- To avoid being struck by lightning, do not stand near trees or tall poles.
- If your hair starts to stand on end, that is a sign of electricity. Drop to your knees and cover your head.
