We’ve recently got some snow over here on the east side of the Valley, and it has made for some wonderful photo ops out in the vineyards. While cold weather can certainly damage vines, grapes are essentially dormant in the winter, and in order to negatively impact vines when they’re in such a state temperatures have to get down to 5° F. (At least when it comes to European varieties; some American varieties are incredibly hardy by comparison, able to survive temperatures down to -30° F.) In the Willamette Valley such temperatures are very rare; on-average, low temperatures around here go no lower than 34° F (in December), as compared to the average low of Sunnyside, Washington (the center of a massive wine growing region in eastern Washington), which clocks in 24° F (also in December).
This lower average means the possibility of an extreme weather event hurting the vines is more likely, but a factor to keep in mind is that snow, somewhat paradoxically, is actually a boon to vines in times of cold weather: a layer of snow can insulate the ground enough to protect the roots, so while the woody trunk might see some damage, the entire plant won’t die. Even so, every seven years or so eastern Washington sees temperatures low enough to kill plants to the ground. However, Washington benefits, in some ways, from cold temperatures: pests usually overwinter in the trunk, finding a cozy spot to nestle into and ride out the cold, but the temperatures get so low in eastern Washington that pests are almost always entirely wiped out. Here in Oregon, our relative balmy temperatures are more survivable, so while we never really have to worry about a brutally cold winter, pests can survive and make a comeback more easily. As with everything involving wine grapes, there are variables upon variables to consider.
In truth, while snow might inspire worries of cold damage, an experienced grape grower knows that by far the worst time of year for cold damage, at least here in Oregon, is actually late summer and early spring, when new buds are beginning to form and the possibility of an unexpected frost could mean a vine loses some or all of its ability to produce fruit. However, we usually dodge that bullet as well: in the Cascade foothills average temperatures in those months are 39° and 42° F. It has been many, many years since we’ve seen any damage from unfortunately-timed freezes. So, feel free to enjoy these pictures of a snow-cloaked vineyard, and rest-assured that our vines are a-okay.