Precipitation Trends & Projections
Pacific Northwest precipitation trends are more variable than temperature trends. Variability is influenced by El Niño-Southern and geography. The total annual precipitation has increased from 1920 to 2000, though not uniformly. Since 1950, variation of ocean salinity has caused wet areas to become wetter and dry areas, like Hawaii, to become dryer. Projections for annual precipitation are less clear but seasonally, most projections show drier summers and increased precipitation during winter and autumn. These changes could influence streamflow flooding, summer water demand, drought stress, and forest fire frequency. Extreme precipitation events are predicted to increase in frequency by some models but not uniformly across the region. Mega-floods that have historically occurred every 200 years are predicted to occur more frequently in a warming climate.
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Last updated: June 3, 2013USFWS Flicker Page