A Historical Look At The Arizona ‘Monsoon’

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Forest fires are burning, parts of the forest have been closed to the public and everyone is wondering the same thing: when will we get rain again? Let’s take a look at Arizona’s “monsoon” and some recent area historical weather data.

The term monsoon is probably a touch misused when describing Arizona’s late summer weather patterns. Dictionary .com’s first definition of monsoon is: “the seasonal wind of the Indian ocean and southern Asia, blowing from the southwest in summer and from the northeast in winter.”

Some will point out that the way Arizona uses the term monsoon is a little bit off, and there is some truth to that, though Dictionary.com’s third definition of monsoon is “any wind that changes directions with the seasons.” And that’s basically what happens in Arizona, the wind changes, bringing in moisture out of the south, leading to summer rains and some very stormy weather conditions.

Historically though, “monsoon” is a relatively newly used term in the region. Old-timers simply called it the summer rains.

The start of Arizona’s monsoon season is now defined as June 15 by the National Weather Service. This is a fairly recent change, as until 2008 the start was defined by three consecutive days of average dew points above 55 degrees. The typical average for this was July 7 in Phoenix, with it starting earlier in other parts of the state including Payson.

Now let’s take a look at Payson weather station data for 1992 to 2010.

This is an imprecise study, since only temperatures and 24-hour rain amounts are available. But for a shot in the dark, let’s take the average of the first of two consecutive days of recorded precipitation, starting June 15. What was the average start date of two consecutive days of recorded rain in Payson during this period? July 4. Out of the 18 observations (note, weather station was down in 2009), 11 out of 18 times two consecutive days of rain were not recorded until July, with the latest observation being July 22 and July 23 of last year. This isn’t to say there isn’t rain earlier. For example last year .10 inches were recorded on July 10 and a trace on July 12.

Now let’s a take quick look at how some old newspaper accounts of how the summer rains were previously greeted.

“A copious rain fell at Payson on the 2nd. It was a roof-soaker and stockmen are jubilant.” — Arizona Silver Belt, July 7, 1894

“To the Belt: Summer rains have set in in the Payson country and there is hopes of good crops and fat cattle. The market is overdone with fruit, melons, vegetables, butter and eggs. The Globe market need have no fears in regard to winter potatoes and apples, for this end of the county will be glad to supply them.” — Arizona Silver Belt, July 15, 1897

“We have had considerable rain, lightning, thunder and high winds during the past two weeks on some places more really than was cared for, as was the case at Gisela, where a cloudburst occurred over Mrs. Hardt’s house, and in five minutes the dwelling was surrounded by two feet of water. The wind did some damage to her barn. No other property at Gisela was damaged.” — Arizona Silver Belt, August 15, 1901

Lastly, I think this last clip best reflects what folks will feel once the rains come.

“The rains have brought gladness where there was depression …” — Arizona Silver Belt, July 28, 1904

Notes

Condolences go to the Wolfe family, the Northern Gila County Historical Society, and the Zane Grey Cabin Foundation on the passing of Marilyn Wolfe. Marilyn was an active member of the community and a major part of the effort to successfully rebuild Zane Grey’s Cabin at Green Valley Park. She will be missed.

Here’s the Web site for neat historical weather data, much of which can be found for free. http://www.ncdc.noaa.gov/oa/ncdc.html

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