Thunderstorm Along North Rim (photo illustration: Brian lane)

The Arizona Monsoon Season officially began on June 15th, 2011.  Last year I had quite a massive response to this posting describing the monsoons, so I thought I would re-post it just to let others know the particulars of this seasonal weather event. Arizonans are remaining hot and dry and there is little evidence that the monsoons will arrive anytime soon, but we know that by July, the afternoon (sometimes severe) thunderstorms will be looming on the horizon. Unless, of course, we get a "non-soon," year where little precipitation is manifested. Lets hope we do recieve a decent amount of rain this year, if nothing else it will help to put out the wildfires currently raging throughout the state. By the way, the "massive response" to this posting last year was really five people - and three of those were spam. Oh, well. 

So, without further ado...

The Arizona Monsoon Season Primer

The Arizona Monsoon Season officially runs from June 15^th through September 30^th. By this standard, now in effect for the last couple of years, we are currently in the monsoon period. But, by the old standard, the monsoonal weather pattern has not yet begun. The old requirements were three consecutive days with dew points over 55 degrees. Only then was a monsoonal flow considered in control of the Arizona climate. So far that has not come to pass, but eventually it will. With that in mind, let’s go over some of the basics that visitors to this area may need to know.

On August 26, 2001 the body of photographer and long-time Grand Canyon hiker George Mancuso (46) was found after he and his hiking partner were caught in a flash flood during Arizona Monsoon Season. Mancuso was a highly experienced canyon traveler and made the cover of Backpacker Magazine as a “Grand Master” of the canyon in 1997. He and his companion had been exploring a side canyon off the Little Colorado River when a violent thunderstorm some thirty miles away, which they probably didn’t even know about, produced a flash flood that caught them in a narrow side canyon and swept them downstream to their deaths. I use this story to quickly illustrate the awesome power and dire circumstances that can be created during monsoon storms.

Monsoon storms are usually highly charged with lightning and produce heavy localized downpours. Enough so that history regularly reminds us how trails can be washed out, much to the chagrin of inner canyon hikers, who then must consider another way of exiting the canyon – when very few exist. The two big issues that one has to deal with during afternoon monsoon storms are lightning and flash floods.

Lightning:

Most lightning strikes the rim of the canyon, the deeper into the canyon you are, the less likely you are to be struck. If you are hiking the canyon’s upper reaches you are still susceptible, so listen for thunder and scan the sky occasionally looking for towering, anvil shaped cumulonimbus clouds. Estimate how far away the storm is by counting the number of seconds after you see a flash of lightning and hear the crack of thunder and divide it by five seconds per mile. Remember lightning strikes can occur ten miles out from the storm front.

If you are caught outside in a lightning storm and hear crackling and/or feel the hair start to rise on the back of your neck quickly crouch down (in the catcher’s position), make yourself small, and cover your head. Do not lie flat, do not huddle in groups (people should be fifteen feet away from each other), avoid wet and damp areas, and avoid standing under tall trees or structures. If you are in your tent you should sit on an insulated mat, and do not touch the walls. Remain in a protected area for a minimum of thirty minutes after the last lightning or thunder is seen or heard.

Flash Floods:

Stay out of canyon washes when storms are forecast. If you must cross a dry creek bed, be aware of escape routes and immediately climb to a point of safety at the first sign or sound of water running down what would normally be a dry wash. Never try to outrun a flash flood.

When driving in Arizona during a monsoon storm…

Do not drive through flooded areas; it takes only a few inches of rushing water to begin moving a vehicle. Arizona has a Stupid Motorist Law that says if you need to be rescued after purposely driving into a flooded wash you will be charged up to $2000. Many such areas are clearly signed “Do not Enter When Flooded” it bodes well to heed that warning.

When the water mixes with grease, oil, and dirt on the road they become slippery so slow down and do not tailgate when driving in a storm. If the storm is so intense that visibility becomes impossible pull completely off the roadway, turn lights off, and take your foot off the brake so that others do not rear end your vehicle (as they may be following your taillights).

Hope that helps a few visitors cope with our Arizona monsoon!


Hike Safe & Have Fun!
Brian