By Rod Hill on 2015-06-10
Portland and Salem are grabbing a spot in weather history for what some may say are all the wrong reasons. A combination of dry weather and near record hot temperatures so early in what is called meteorological summer may have bad consequences down the road as fire season looms.
Let's begin with Portland's lack of spring rainfall. Dating back to April 1st, PDX has seen 2.74" of moisture, a total less than 50% of normal. With forecast charts showing little chance of significant rainfall through the end of June, Portland may go into summer with the least amount of April-June rainfall in more than 30 years! It is a well known climate fact, that metro valley precipitation in July and August comes primarily in scattered showers and thunderstorms and can total next to zero for each month. In other words, as fire season begins, Portland may be looking at a 5-month period of limited rainfall and increasingly dry conditions through August. The driest April - June on record at PDX occurred back in 1987, when only 3.71" of rain fell. I project this year's total will be 2.94" or less.
As for our 4-day heat wave, last Saturday through Tuesday, the National Weather Service reports it is one of the earliest stretches of 90 degree heat on record! The graphic shows Salem's run of four 90 degree days, including a high of 96 is the longest, early run of heat in 120 years! Portland hit 90 or higher three days in a row, becoming just the 4th such early heat wave in the last 75 years.
As to what it all means as we look forward, the answer is uncertain. Portland's summer rainfall is very sporadic and extremely dry weather is typical. Several temperature outlooks call for the Northwest to see well above normal summer temperatures. However, I believe it is unlikely that Portland will approach last year's total of 21 days reaching 90 or hotter.
Meteorologist Rod Hill
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