Today (Jun 15th) kicks off the start of the Arizona Monsoon. Why is it called a monsoon? The winds shift. During winter, the primary wind flow is from the west or northwest (CA and NV). But during summer, the winds shift to a southerly or southeasterly direction. Moisture streams northward from the Pacific Ocean and the Gulf of Mexico producing a radical change in moisture conditions statewide. (In other words … we get sticky stuff called humidity … ugh.)
Up until 2008 the beginning of the monsoon was determined by having 3 consecutive days with dew points of 55 degrees or greater. Two years ago the National Weather Service changed it to set dates … Jun 15 thru Sep 30. The average start (when action happens) is around mid-July.
We live in Tucson – which is completely surrounded by mountains – so get awesome views during monsoon. By mid-afternoon the huge billowy clouds begin forming over the mountains and by late afternoon the rains and rumblings begin. Storms can go into the night hours with some incredible light shows all across the city as storms move away from the peaks back down into the valley as temps cool. Our backyard looks out over 2 large mountain ranges (Rincons are over 8,000 ft and the Catalinas are over 9,000 ft) with foothills connecting them so lightning shows are spectacular. But that also means many potential wildfires since many dry lightning storms during monsoon.
The average monsoon rainfall depends on what part of the state you live in. For example, between Jul, Aug and Sep Phoenix’s normal rainfall is 2.65 inches. Tucson averages a little over 6 inches of rainfall during the 3-month period while Greer, in the White Mountains, averages 11.46 inches. By contrast, Yuma averages only 1.21.
…the name “monsoon” is derived from the Arabic word “mausim” which means “season” or “wind-shift”?!
…two-thirds of all of Arizona’s annual lightning strikes occur between June and August?!
…altho Arizona rarely experiences a tornado, we get an average of 4 every year?! And thunderstorm-generated winds can exceed 100 mph over a fairly large area so may look like tornado damage.
…thunderstorm wind gusts in Arizona almost always exceed 40 mph?!
…dust storms (also called haboobs) usually last 15-30 minutes but can go up to an hour?!
…6 inches of moving water can knock you off your feet and 2 ft can float a car?!
…Arizona has a “stupid motorist law”?! Basically if a driver becomes stranded after driving around barricades to enter a flooded stretch of roadway, they can be charged for the cost of his/her rescue up to $2,000.
Some basic commonsense safety tips…
- Flash floods are common during monsoon. If road signs, barricades or cones are placed in areas … turn around and find another way or you may get fined.
- Floodwaters should be avoided until local authorities say “all clear” since they may be contaminated by oil, gas or raw sewage, or may be electrically charged from underground or downed power lines.
- If driving when you encounter a dust storm, pull off the road immediately. Turn off your headlights and taillights, put your vehicle in “PARK,” and take your foot off the brake. Other motorists may tend to follow taillights in an attempt to get through the dust storm, and may smash your vehicle from behind.
- Consider securing loose outdoor furniture and garbage cans before storms hit to lessen flying debris.
- Be aware of lightning and wildfires.
Stay tuned since Lightning Safety Awareness week is coming up so posting some lightning statistics and tips here soon.
Additional resources:
Arizona Monsoon Safety page
ASU School of Geographical Sciences & Urban Planning – Basics of Arizona Monsoon
NOAA NWS Phoenix Monsoon Safety page
NWS Flagstaff (Northern AZ) Weather page
NWS Tucson Monsoon page
Some great monsoon lightning / dust storm photos from Ultimate Chase
Short animation of monsoon called Demystifying Monsoon (by AZ Republic)
photos from Arizona Active Retirement Living blog and a dipity page
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