While technically it’s not quite summer, we all know what to expect. The rule I’ve so often heard announced by locals is to not expect consistently nice weather until around the Fourth of July. Whether or not this holds true as climate change bites at our heels, summer in the Pacific Northwest is reliably dry. Capitol Hill is the same, despite our sense that things are different up here.
Say the word Mediterranean and one imagines sun drenched Italian shores, olive trees, and Vespas. With the exception of the latter, we don’t have such icons, but as a description of our climate it’s broadly accurate. We have wet, mild winters that lead into an extended dry period in the summer.
Now remember that weather is not climate. Climate is a complex analysis of trends in weather. Climate informs the way our plants and animals live, weather may dictate an immediate response. Our native species do a great job of dealing with dry periods. The Pacific Madrone (Arbutus menziesii), my favorite broad-leaved evergreen tree, goes about replacement of leaves during the dryer times of the year. This favors water retention in the rocky, well drained soil it favors as leaves exposed to sunlight are good at photosynthesizing but also easily loose moisture. This and other adaptations make it drought tolerant.
Drought may seem a caustic or excessive descriptor for people from California or Texas, but we do indeed have an annual, albeit short, respite from rain which could be called drought. The reality is that Seattle is ranked 44th for annual rainfall in US cities, with average of 38 inches. We experience this because of the annual switches in large-scale atmospheric circulation over the Pacific that sends less moisture our way (learn more here). Combined with the slight rainshadow of the Olympic range, leads to reduced precipitation. Luckily for us, as Pacific moisture reaches the peaks of the Cascades it is forced to fall as snow and rain, giving us our fresh water supply, to be stored in reservoirs like the one under Cal Anderson Park.
As I mentioned before, June is often actually quite cloudy and gloomy. This year we’ve actually had an easier go of things. Our current spell of sun is simply due to a stronger high pressure system over the Pacific than usual (I’ll leave Cliff Mass to explain that for you).
Do we have ultra-local climate on Capitol Hill? This column being about the natural history of the Hill, it makes sense to try to answer this question. However, while there may be trends that give us slight differences, we don’t experience markedly different climate from the rest of Seattle. We do receive slightly more rain, from air moving Eastward because as air moves up in elevation, it cools, condenses, and can’t hold as much moisture. Our seat atop the hill catches a little more precipitation than adjacent low-lying areas, but not by much.
As we head into summer there will inevitably we times we get too hot. All the cement around doesn’t do us any favors. If you’ve ever stood in full sun in a parking lot or walked down broadway in the afternoon, you’ll know what I mean. Escaping to the green shade or finding something that doesn’t radiate so much solar energy is a good tactic. We have nearby bodies of water that moderate heat well, an escape to Lake Washington or Puget Sound will cool you off. Large bodies of water are excellent heat sinks, tucking it away and keeping things cooler on their shores. It’s a good thing too, us hot weather mossy-backed wimps, need places to hide in the sweltering 70s.
Previously in Pikes/Pines