2008's first triple-digit temperature was late in getting here, but making up for it is the heat's intensity.
Summer informally arrived at 12:39 p.m. Sunday, when the Valley's official thermometer reached 100 degrees. More than three hours later, the temperature maxed out at 105 - 11 degrees above normal but two degrees shy of the day's record.
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Around the East Valley, airports in Chandler, Scottsdale and Mesa (Williams Gateway) reported highs of 102.
And the National Weather Service expects this belated heat wave to strengthen. The forecast highs for today and Tuesday are 108 and 109, respectively, which would break the previous daily records by three degrees.
In preparation, the Weather Service has issued an excessive heat warning for today and a watch for Tuesday. The latter will likely be upgraded to a warning, the forecasters acknowledged.
According to the agency's climate records for Phoenix, which go back to 1985, the first 100-degree reading was five days later than usual. When considering only the last 30 years, to account for the Valley's urban sprawl, on average the first 100-degree day was May 1.
In fact, this is the latest debut of 100 degrees since 1999, and the fourth-latest in the last 25 years.
What's to explain why the heat came so late?
"Normal climatological cycles," Weather Service meteorologist Mike Bruce said Sunday afternoon.
In other words, this is nothing but the vagaries of weather.
As Bruce noted, the temperature reached 99 on April 29. No, 99 degrees is not 100, but looking deeply at the difference "is trying to split hairs," he said.
If Phoenix's historic average holds up, with three straight days of triple-digit highs this would mean Valley residents will endure just another 107 days of 100-degree temperatures this year.
But in the short term, relief is on the way.
A powerful storm system is forecast to dive across the West, and predictions call for it to drastically turn down the heat and turn up the wind.
"Being May, the chances of any widespread precipitation are still pretty slim," Bruce said. "But we could see isolated storms in the mountains, as we saw this past week."
Thursday, an unseasonable thunderstorm rolled out of the high country to the Valley's northeast and rumbled through Apache Junction, east Mesa, Gilbert, Queen Creek, Chandler and beyond. The whipping winds knocked out power and raised a wall of dust that limited visibility to nearly nothing.
That weather system also dropped 11 inches of snow at Sunset Crater near Flagstaff. The forecast calls for a chance of snow showers in Arizona's highest elevations from Wednesday through Friday.
Back in the Valley, the highs on Thursday through Saturday will drop into the upper 80s.
