John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
It’s drier near the water, because the city’s weather makes no sense.
When Seattleites talk on the phone, it’s not too rare for one person to complain about the drizzle and the other to say, “But it’s sunny here." The city is notorious for its microclimates—stark but small geographic divides in temperature and precipitation that seem to flaunt the laws of weather.
Now the city has produced a map outlining the borders of these various wet and
dry not-quite-as-soggy zones. Seattle Public Utilities took historical averages from 17 rain gauges, and found areas along the downtown waterfront are oddly less sodden than the northern and southern parts of town. Folks living in Belltown can expect an average of 32 inches of rain a year, for example, whereas those in Rainier Beach face 40 inches of H2O.
Meteorologist Scott Sistek of KOMO News spoke with the utility department’s resident weather guy (yes, it actually hired one) to discuss the variations in local climate. The less-wetness of the northern areas is partly attributed to the Olympic Rain Shadow, a phenomenon in which the Olympic Mountains rob northeast-traveling air of moisture. (This topographic interaction is the reason why the mountains’ west-facing valleys are verdant with mossy rain forests.) Here’s more from Sistek’s discussion:
On the other hand, SPU meteorologist James Rufo-Hill says Rainier Beach and southeast Seattle also gets a little extra rain from the opposite effect—air ramping up the Issaquah foothills. Rising air causes condensation and squeezes out additional rainfall—it’s why parts of the Cascade foothills get about double the annual rain as Seattle. The Issaquah hills aren't as tall, but enough to give a little extra rain to the Eastside, and yes, to the far eastern edges of Seattle. …
And on the dry side, some of the Seattle hills create mini-rain-shadows on their lee side.
“Even within the Seattle’s city limits, there are microclimates and small-scale rain shadows," Rufo-Hill said. "SPU’s rain gauges have shown that when winds are southwesterly, a small rain shadow often forms over downtown Ballard, which is in the shadow of Magnolia. Similar patterns are consistently observed downwind of West Seattle and Capitol Hill, which can keep communities along the Duwamish River and Lake Washington, respectively, drier than surrounding neighborhoods."
For locals, trying to escape the rain by moving seems like an impossible feat. Head north and you’ll have lighter rain more often, says Sistek, but go south and you’ll get poured on less frequently but harder. When it comes down to desperately trying to minimize your moistness, he suggests a “small break” might be found east or northeast of a hill, where the topography takes a teeny bit of sting out of the foul weather.