Weathercatch: The leaves they are a changin' – how the weather helped

<p><p>As we wrap up the first half of October, autumn colors are spectacular in our region. Bursts of orange, red and yellow in trees are putting on an especially good show this season.</p></p><p><p>Why is that?</p></p><p><p>The primary reason that leaves change from green to autumn colors is a biochemical process caused by decreasing daylight. But when this change occurs, the intensity of the colors and how long they last depends largely on weather conditions, which vary from year to year.</p></p><p><p>This year, the weather has contributed to fall foliage at its finest.</p></p><p><p>Conditions that produce the most impressive displays include mild, sunny days and cool nights without hard freezes, according to the U.S. Forest Service website “Science of fall colors.”</p></p><p><p>So far, we’ve experienced plenty of mild temperatures, sunshine and not-too-chilly nights. In Spokane, the first half of October saw a number of days with temperatures in the 60s and even into the low 70s. Only recently did we see the mercury dip into the low 50s. Overnight lows ran mainly in the low 40s – cool, but not cold enough to cause frost – until early this week.</p></p><p><p>The amount of moisture in the soil also impacts our region’s autumn leaf show. Trees need water. Without it, they go into survival mode and shed withered leaves before they can change color. The extreme drought we experienced this summer could have doomed our fall foliage. Instead, much-needed rainfall that came in September helped replenish the trees’ dry root systems. A total of 1.35 inches fell last month – almost as much as the six previous months combined.</p></p><p><p>Heavy winds, strong rains and a big snowfall can also cut the season short. Last year’s record-breaking 6.9 inches of snow in Spokane on Oct. 23 took down an abundance of leaves from their branches. Not only did we have to shovel snow but we also had plenty of leaves to rake.</p></p><p><p>The brilliantly colored trees of New England make it the country’s premiere fall foliage destination. What do they have that our region doesn’t? A far greater number of deciduous trees. Mixed in with our maples, aspens and larches are lots of evergreen trees as well. Here in the Spokane area, this includes the grand ponderosa pine (the city’s official tree) and the Douglas fir. All of which means, New England’s autumn show may be show-offy, but ours is darned good.</p></p><p><p>A cold front that moved in on Sunday of this week ushered in some winds, frost and a chance of rain and snow but not enough to destroy our autumn show. A fair-weather system building over the region is expected to bring partly-sunny skies and temperatures in the upper 50s this weekend, with a slight chance of some light rain.</p></p><p><p>With Mother Nature continuing to cooperate, it’s a good time to get outside and view the landscape in its full fall splendor.</p></p><p><p>———</p></p><p><p><em>Nic Loyd is a meteorologist in Washington state. Linda Weiford is a writer in Moscow, Idaho, who’s also a weather geek. Contact:</em></p></p>