2008 marks 14th-wettest year for Valley


January 4, 2009 - 5:20PM

2008 marks 14th-wettest year for Valley

Mike Branom, Tribune

For the Valley to endure more warm weather in 2008 was not surprising. But most unexpected was rain falling in amounts not seen for a decade.

With an official precipitation total of 9.58 inches, Phoenix had its 14th-wettest year on record, according to the National Weather Service. That was 25 percent more than the average of 7.66 inches, and the most rain since 1998.

Most of the rain could be credited to a soaking monsoon season. From mid-June through the end of September, the Valley’s official gauge took in 5.7 inches. That made last summer the wettest since 1984 and the 10th-wettest overall.

Looking at the thermometer, the heat was on.

The average temperature was 75.4 degrees, which was 1.2 degrees above normal and tied with 1992 for the 11th-warmest in more than 110 years of record-keeping. But this was a cool-down from 2007, when the yearly mean was 76.4 degrees – the Valley’s second-hottest year. Overnight low temperatures averaged out to 63.8 degrees, ninth-warmest overall.

Finally, 2008’s average daytime high was 86.9 degrees, 17th-warmest on record.

Weather experts say the temperatures in the Valley, especially at night, are rising due to the effect known as the urban heat island. During the day, heat is trapped in the region’s asphalt, concrete and stucco; at night, these materials are slower to cool than, say, untouched desert land.

Why 2008’s drenching came as a surprise can be explained by the drought gripping Arizona since the mid-1990s.

Nine of the last 13 years have seen below-average rainfall. In fact, the total for 2008 wasn’t much lower than the combined amount for the previous two years (10.5 inches).

But last year started off wet, with a January that had almost twice as much rain as usual. That gave 2008 a cushion to work with in a late winter/early spring period that was very dry. Then in late May, a shockingly strong and unseasonable storm hit Arizona.

By mid-July, the monsoon was in full swing. In an average monsoon, the rainfall total is 2.77 inches. But that mark was passed in early August.


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