Late summer heat and lingering mild weather in October have helped make up for a slow start to the Inland Northwest’s growing season.
The current spell of warm days and cool nights is also setting the stage for a great show of autumn leaf color. These are the conditions that cause leaves to stop photosynthesis and take on the warm hues of the season.
Area gardeners are happy, because crops that were slow to develop this year are getting extra time on the vine with an absence of freezing weather.
The growing season “started out slow,” said Bob Mauk, gardening expert at Northwest Seed and Pet in Spokane, but “we’ve probably had an extra month of weather that has extended the season.”
The first half of 2011 was remarkably cool, with below-normal temperatures recorded from February through July.
Spokane’s summer was absent any serious heat – temperatures never reached the upper 90s. The first 90-degree day didn’t arrive until July 6.
The warmest temperature for the year, at 94 degrees, came Aug. 28.
Yet September was nearly 5 degrees above normal in Spokane, which brought seven days of 90-degree or warmer temperatures. Walla Walla had an average high of 82.3 degrees last month, the warmest September in nearly two decades.
Kent Waliser, general manager of Sagemoor Vineyards north of Pasco, said wine grapes were two to three weeks behind normal.
Grape harvesting was only about 40 percent complete last week, said Waliser, chairman of the Washington Wine Commission. His company supplies fruit to Arbor Crest and Barrister, two Spokane wineries.
He added, “I think things are going to be fine. In the next two to three weeks, the majority of the wine grapes will get picked.”
Washington State University reported last week that the wine grape and pear crops were 10 days behind schedule and that apples were two weeks late.
Forecasters said the rest of autumn is likely to be wetter than normal, which should mean the relatively mild conditions will continue.
October can be fickle, offering the chance of a mild Indian summer or an early freeze.
Some outlying areas have seen frost, but most parts of Spokane and Coeur d’Alene have been frost-free so far.
In Spokane, the average date of the first frost is Oct. 7. Over the past 10 years, the first frost has occurred as early as Sept. 29 and as late as Nov. 2.
In 2009, Spokane saw record lows of 23 and 20 degrees on Oct. 10 and Oct. 11, respectively. In 2002, the thermometer dropped to 7 degrees on Halloween.
Weather records show that the earliest freezing temperature on record in Spokane came Sept. 10, 1895. The latest frost on record was on Nov. 11, 1944.