72 Microseasons of the Pacific Northwest

By mid-to-late July, wildfire smoke has become one of the most visible and region-altering natural phenomena of the Pacific Northwest summer. Ignitions typically begin in the dry interior east of the Cascades — particularly in the Okanogan Highlands, Methow Valley, and eastern Oregon's Blue Mountains — but smoke travels hundreds of miles, affecting air quality across all six regions. The sky loses its summer blue, the sun takes on a deep orange-red cast that makes for eerie sunsets and sunrises, and the mountains disappear behind a whitish haze even on otherwise dry, rain-free days. Smoke plumes from the largest fires — a feature increasingly associated with this time of year — can generate their own weather. Pyrocumulus clouds (also called "fire clouds") billow vertically above the most intense blazes, sometimes reaching 30,000 feet and visible from Seattle or Portland as distinct vertical columns on an otherwise clear horizon. In especially active fire years (2017, 2018, 2020, 2021 were all significant), entire mountain ranges such as the North Cascades or Okanogan Highlands are obscured for weeks. The haze layer often traps in valleys overnight — the Willamette Valley, Puget Sound lowlands, and the BC Lower Mainland can wake to near-zero visibility mornings that clear as afternoon upslope winds develop. For naturalists, smoke season marks a measurable shift in ecology. Pollinator activity drops on high-smoke days as insects and hummingbirds reduce foraging. Birds respond to rapidly changing conditions. On the human calendar, the onset of reliable smoke is one of the clearest signals that high summer has arrived and fall is approaching. Monitoring resources like the Washington Smoke Blog (wasmoke.blogspot.com) and USFS InciWeb track active fires and smoke forecasts, and have become routine daily checks for millions of Pacific Northwest residents from July through September.