Record Drought Impacting the Pacific Northwest

The Western US is currently experiencing some of the most severe drought conditions on record. You can see it in the brown grass across the Leschi neighborhood, the explosive wildfires currently scorching Northern California, the bone-dry reservoirs across Southern Oregon and much of California, and the desiccated branches of deciduous and coniferous trees throughout the Pacific Northwest. This past spring was one of the driest on record for much of the Pacific Northwest, and this summer has been one of the hottest & driest summers on record and was punctuated by a heat wave in late June that was far stronger than any Pacific Northwest heat wave in recorded history.

This latest drought is just the most recent episode of a decade that has been defined by droughts across the Western US. Late 2011–14 was the driest period in California’s recorded history, and the drought persisted until early 2017, when a series of strong atmospheric rivers moved and brought extreme flooding to portions of the state. California’s drought spread north into the Pacific Northwest, and 2015 experienced historical drought conditions due to the combination of very little mountain snowpack during the 2014–2015 winter and extreme heat during the 2015 summer. I was a camp counselor up at Hidden Valley Camp in near Granite Falls, WA during the summer of 2015 and remember how hot and dusty that summer was. There was so much dust, my tent group and I were inspired to do a skit re-enacting the “Dust Bowl” (I was the cranky farmer, of course).

This most recent drought formed in summer 2020 due to hot/dry weather over the Pacific Northwest and a well-below-average monsoon season for the Desert Southwest. La Nina conditions during the 2020–21 winter resulted in well-below-average precipitation and worsening drought for California and the Desert Southwest, and many locations in the Pacific Northwest and California saw their driest spring on record. Coupled with the continued hot and dry conditions we’ve seen this summer, many places across the Western US are now experiencing some of their most severe drought conditions in modern history.

The Western US is no stranger to drought. Using tree rings as a proxy for rainfall/vegetation growth, climate scientists have found that the Western US has experienced many periods of multi-year drought over the past millennium. But the past two decades have seen a marked increase in the expanse and severity of drought over the Western U.S. relative to most of the 20th century. In California, reservoirs are consistently setting all-time low records and water usage restrictions are becoming an annual occurrence, and many of the largest fires in recorded history for California and the Pacific Northwest have burnt in just 2020 and 2021. And anecdotally, it seems like recent summers have consistently been much smokier than they ever were in the 2000s, during my formative years in the Leschi neighborhood.

Drought is not just dependent on the amount of rainfall; it is also dependent on the rate at which this rain evaporates back into the atmosphere. According to climate scientist Dr. Daniel Swain at UCLA, approximately half of the severity of the current “megadrought” over the Western US can be attributed to warming temperatures alone, and without the warming, the drought would be much less severe. This means that as global temperatures rise, droughts will become more common and more severe, even without any change in precipitation. Areas like Western Washington have more water resources and more ability to adapt to drought, but areas like southern California, that have much lower resources and a much higher population, will have face some serious challenges in adapting to a world with more severe drought.

Unfortunately, autumn is peak fire season for California due to the increased occurrence and intensity of strong, extremely dry Santa Ana and Diablo winds and continued drying of fuels during this time, so I fear that this could be a particularly active autumn/early winter for fires in for California. For the Pacific Northwest, September tends to be the month with the highest potential for large, destructive wildfires west of the Cascade crest, and that risk is particularly high this year due to how dry fuels are. Still, it’s too early to tell if we’ll see a fire weather pattern this month, with strong, dry offshore flow. Let’s hope that we get plenty of rain this autumn to help moisten fuels, and that any offshore flow holds off until the fire danger environment is relatively low.

~Charlie Phillips

Charlie Phillips is a Madrona resident who received his B.S. in atmospheric sciences from the University of Washington. He works in Portland as a meteorologist. Check out his weather website at Charlie.weathertogether.net.