Many regular readers of this column are aware of the effects of La Niña, and variations in the El Niño-Southern Oscillation (ENSO) in general, on the overall weather of the Pacific Northwest during the cool season. Nevertheless, it bears repeating that La Niña is often (but not always!) accompanied by relatively cool and wet winter weather in an overall sense, and a healthy snowpack going into spring.| Washington State Climate Office
The La Niña Watch issued by the Climate Prediction Center in August is still in effect. The “watch” means that La Niña conditions are likely to develop over the next several months, but that La Niña conditions are not currently in place. The probability of La Niña is between 65 and 71% for the periods of September-October-December through November-December-January. La Niña is the most likely outcome for the December-January-February period, but chances decrease to 51%.| Washington State Climate Office
September 2025 was the warmest September on record in Washington back to at least 1979 and likely the warmest on record back to 1895*. Temperatures were +5.7°F* warmer than normal when averaged statewide. Much warmer than normal temperatures observed across the eastern slopes of the Cascades and across much of eastern Washington. In these warmest areas, temperatures were nearly 5-8°F above normal.| Washington State Climate Office
WHEN: November 4, 2025 7:30 am-4 pm PT (8:30 am to 5 pm MT) WHERE: In person at Boise State University or Limited Virtual Please register by October 30 to ensure an accurate catering count. The Idaho Department of Water Resources and Boise State University will host the Pacific Northwest Water Summit to identify vulnerabilities and opportunities to increase drought and climate resilience across economic sectors that depend on the region’s water resources.| Washington State Climate Office
Happy 2026 Water Year! Now that water year 2025 is complete, we want to hear from you! How was the Pacific Northwest (Washington, Oregon, and Idaho) impacted? We encourage you to fill out the PNW Water Year 2025 Impacts Survey. The goal of this survey is to gather information about impacts and response actions that were implemented during the 2025 water year (October 1, 2024 – September 30, 2025) due to either abnormally dry or abnormally wet conditions.| Washington State Climate Office
Streamflow deteriorated during September as a result of warmer than normal temperatures and a relatively slow start to the rainy season. A map of September streamflow percentiles by watershed reveals that the vast majority of watersheds are below normal or much below normal, seen in orange and brick red shading. Notably, multiple watersheds in the Cascades including the Upper Yakima watershed are near record low streamflow levels (bright red shading).| Washington State Climate Office
September was once again a warmer than average month statewide. This was especially true across eastern Washington where prolonged warm spells with particularly warm overnight temperatures led to anomalies of around 5-8°F above normal. In western Washington, a brief single-day heat wave occurred on the 16th as a strong ridge built over the region. This warm day is clearly visible as a mid-month spike on the above graph of SeaTac’s daily temperatures.| Washington State Climate Office
Summers in western Washington have historically been quite mild, but extreme heat has become much more common in the past couple of decades. In July of 2009, temperatures soared to 103°F in Seattle and some locations around Puget Sound rose to 100°F for the first time in recorded history. A mere decade later, during the heat wave of June 2021, temperatures rose to 108°F in Seattle and 116°F in Portland marking unprecedented summer record temperatures for both cities.| Washington State Climate Office
What’s Next for the Pacific Northwest? Slight chances of above normal precipitation and temperatures for October 2025. The Climate Prediction Center’s monthly outlook for October 2025 looks to be warm across the interior western United States with a slight chance (33-40%) of warmer than normal temperatures extending up into Washington State. As weak La Niña conditions continue to develop in the Tropical Pacific, odds have tilted in favor of above normal precipitation across the state as ...| Washington State Climate Office
What’s Next for the Pacific Northwest?| climate.uw.edu
If you have lived in Washington for long enough, you are probably well aware that our dry and sunny summers end predictably around October or early November when fall rains and cloud cover move in. This enduring feature of Washington’s climate is not only important to upholding our internationally-recognized mysterious and moody PNW persona, but it also supports ecosystems (and us humans) that rely on and have adapted to this consistent and timely precipitation cycle.| Washington State Climate Office
Late August Climate Outlook| Washington State Climate Office
June 2025 Climate Summary| Washington State Climate Office