Rain in Seattle in Oct 2026? — Above 2 inches

- [2026-10-13] Official CLISEA (Sea-Tac) month-to-date precipitation was 0.06" through 5 pm on Oct 13. The 1991–2020 normal to date is 1.26", so the month is 1.20" below normal. Oct 13 itself recorded only a trace. The report was issued at 6:19 pm PDT. Rain needed for a "Yes" is more than 1.94" over Oct 14–31. https://forecast.weather.gov/product.php?site=SEW&product=CLI&issuedby=SEA - [2026-10-13] The same report puts the water year since Jan 1 at 21.65", against a normal of 24.66" (−3.01"). Last year's figure to date was 16.87". https://forecast.weather.gov/product.php?site=SEW&product=CLI&issuedby=SEA - [2026-10-10] The earlier CLISEA report (for Oct 9) showed light rain that day and a 58°F high. Only 0.06" has accumulated since Oct 1, so the first 13 days were almost entirely dry. https://forecast.forecast.weather.gov/product.php?site=NWS&product=CLI&issuedby=SEA - [2026-10-12] FOX 13 forecast a mainly dry workweek through Friday Oct 16. Offshore flow was expected to push highs to the mid-60s to mid-70s on Friday. Western Washington was under high-pressure ridging Wed night–Fri. https://www.fox13seattle.com/weather/seattle-weather-feeling-like-summer-later-week - [2026-10-12] FOX 13 said a weakening system would bring a chance of rain Fri night–Sat (Oct 16–17), mostly along the north coast and North Cascades. It said "another, potentially more organized system" could reach the coast Sunday Oct 18. No amounts were given. https://www.fox13seattle.com/weather/seattle-weather-feeling-like-summer-later-week - [2026-10-13] The NWS Sea-Tac point forecast (updated 1:15 pm Oct 13) has a 20% chance of rain before 8 am Wed Oct 14, then mostly sunny. Thursday–Friday are dry (Fri high near 73). A chance of rain starts after 11 pm Friday and continues Saturday, mainly before 11 am. I found no quantitative precipitation amount for Sea-Tac. https://www.weather.gov/98188 - [2026-10-13] The Seattle (47.62N) point forecast lists a 30% chance of rain after 11 pm Friday and rain chances through Sunday–Monday (Oct 18–19). The Sunday high is near 55. https://forecast.weather.gov/MapClick.php?lat=47.6218&lon=-122.3503 - [2026-10-10] A frost advisory was in effect for Sea-Tac on Oct 12, 12–8 am. The NWS forecast then showed sunny weather Oct 11–14. https://forecast.weather.gov/MapClick.php?lat=47.449&lon=-122.3093 - Climatology: the 1991–2020 Sea-Tac October normal is 4.44" over about 14 rainy days. A site citing the NOAA normals (Seek Seattle, 2026 guide) gives this. About 3.2" of the normal falls in Oct 14–31 (4.44 minus 1.26 for Oct 1–13). That is my arithmetic, not a sourced figure. https://seekseattle.com/when-does-rain-start-in-seattle-2026-rainy-season-guide/ - [2026-10-12] The first scheduled wet signal is Oct 16–18. Sea-Tac forecasts through Oct 19 show only light, chance-level rain. The remaining 12 days (Oct 20–31) are beyond reliable deterministic forecast range. The resolution source is the NWS CLISEA daily climate report for Sea-Tac. The market uses "strictly greater than 2 inches", and the official monthly total is the figure that counts. BOTTOM LINE: Official Sea-Tac rainfall is only 0.06" through Oct 13, so a "Yes" needs more than 1.94" over Oct 14–31. The next 3–5 days are mostly dry, with only light rain chances from Oct 16–19. The outcome therefore depends on a wetter-than-normal pattern in the last ~12 days of the month (Oct 20–31). NOT FOUND: NWS or WPC quantitative precipitation forecasts for Oct 18–31 for Sea-Tac. The CPC 8–14 day and week 3–4 outlooks. The NWS Seattle forecast discussion text. Any Oct 14 CLISEA update. Other venues' or sibling-strike prices.

- [2026-10-13] Sea-Tac (CLISEA) month-to-date precipitation was 0.06" through Oct 13, against a normal of 1.26" (−1.20"). Oct 13 itself had only a trace. The market therefore needs more than 1.94" over Oct 14–31, with the 1991–2020 normal for the rest of the month about 2.6". https://forecast.weather.gov/product.php?site=SEW&product=CLI&issuedby=SEA - [2026-10-10] The Oct 9 CLISEA showed 0.01" month-to-date. The month has been very dry so far. The CLI report is the settlement source. https://forecast.weather.gov/product.php?site=NWS&product=CLI&issuedby=SEA - [2026-10-14] The 1991–2020 Sea-Tac October normal is about 3.9", with about 14 days of measurable precipitation. Another source says the middle half of Octobers fall between 2.5" and 5.1". https://www.currentresults.com/Weather/Washington/Places/seattle-weather-in-october.php - [2026-10-14] Historical Sea-Tac October totals, 1941–2025 (85 years), come from the extremeweatherwatch table. By my count, 68 of 85 were strictly above 2.00", about 80%. Years at or below 2.00" include 2013 (1.54), 2006 (1.55), 2002 (0.67), 1993, 1991, 1987 and 1974 (1.99). https://www.extremeweatherwatch.com/cities/seattle/month-october/monthly-precipitation - [2026-10-14] In the last 30 Octobers (1996–2025), 27 were above 2.00" (90%). The only misses were 2002, 2006 and 2013. The last 5 years were 3.70, 3.04, 2.89, 2.51 and 5.76; 2020 was 2.58. Several were close to the line (2008 at 2.17, 2022 at 2.51). https://www.extremeweatherwatch.com/cities/seattle/month-october/monthly-precipitation - [2026-10-14] This analogue does not condition on a dry start. The table has only monthly totals, so how many of those 68 years had under 0.1" by Oct 13 cannot be read from it. The unconditional base rate overstates the chance this year because roughly 40% of a typical month's rain has not fallen. Reaching 2" needs roughly 75% of the normal for the remaining 18 days. - [2026-10-06] The UW Washington State Climate Office early-October outlook says El Niño is intensifying, with record-breaking SST anomalies. The CPC 1-month October outlook shows elevated chances of warmer and drier than normal conditions across much of the state. https://climate.uw.edu/washingtons-climate/climate-outlook/ - [2026-10-07] NWCC Predictive Services (CPC data) say CPC leans warmer and drier for October in the Pacific Northwest. September was also very dry. El Niño tends to shift the storm track south. https://gacc.nifc.gov/nwcc/content/products/fwx/MonthlySeasonal.pdf - [2026-10-13] Hoodline's local forecast (a media summary of NWS data) has cloudy weather Tuesday, warmth Thursday–Friday, then rain chances from Friday night through Monday (Oct 16–19). No rainfall totals were given. https://hoodline.com/2026/10/seattle-sun-tease-two-day-warmup-before-weekend-washout/ - [2026-10-14] The Old Farmer's Almanac (low-skill, not a dynamical forecast) predicts about 3" for the month, with sunny weather Oct 4–17, showers Oct 18–23 and isolated showers Oct 24–31. https://www.almanac.com/weather/longrange/wa/seattle - [2026-10-14] The Aug 20 CPC long-lead discussion said a very strong El Niño was more than 90% likely this fall and winter. It tilted Sept–Nov precipitation toward below normal across northern and eastern Washington, with no strong signal for Puget Sound. https://www.cpc.ncep.noaa.gov/products/predictions/long_range/lead14/fxus05.html - [2026-10-14] Wet extremes show late-month storms can reach 2" in one event. Sea-Tac recorded 1.99" in a single day on Oct 28, 2021, and the 2003 daily record was 2.19". Late October atmospheric-river or windstorm events are the main path to YES from here. https://sites.uw.edu/theuwdawgcast/2021/10 BOTTOM LINE: The unconditional base rate for Oct > 2" at Sea-Tac is high (about 80% since 1941, about 90% in the last 30 years). This year is a dry outlier case, with 0.06" through Oct 13, a CPC lean to dry, and a strong El Niño, so the outcome depends on whether the remaining 18 days produce about 1.95" (roughly 75% of normal for that span). The forecaster should discount the base rate substantially and weigh the forecast rain around Oct 16–19 and any late-month storms. NOT FOUND: Quantitative NWS/WPC rainfall totals for Oct 16–19 or beyond. A historical conditional analogue of Octobers that were dry through the 13th. Any CPC probability specific to Sea-Tac for the Oct 14–31 span. The market's own price (deliberately not searched for).

YES means: Official CLISEA (Sea-Tac) total precipitation for October 2026 is strictly greater than 2.00", i.e. more than about 1.94" falls Oct 14–31. - [2026-10-13] The NWS Seattle AFD (810 pm Oct 13) has a pattern flip to unsettled after the Thursday–Friday ridge. A trough digs south from Alaska, and "a couple of systems" cross the area Saturday Oct 17 and late Sunday through Tuesday Oct 18–20. The second system is "cooler and wetter overall", spread over about 48 hours, with snow levels falling to 5,000 ft. Seas reach 10–14 ft Monday, which signals a real frontal system. The first system is quick, and only a few north Cascade spots may get up to 1". The AFD gives no Sea-Tac amounts. https://forecast.weather.gov/product.php?site=NWS&issuedby=SEW&product=AFD&format=CI&version=1&glossary=1&highlight=off - [2026-10-13] The CPC 6–10 day discussion (Oct 19–23) rates confidence above average (4 of 5). It has a weak trough along the West Coast and above-normal precipitation favored across much of the West. This supports a wet Oct 19–23 start. https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html - [2026-10-13] The CPC 8–14 day outlook (Oct 21–27) puts Washington at near-normal precipitation, with the Pacific Northwest coast "near-normal… behind the mid-level trough axis". Near-normal is not dry. The prior Oct 12 discussion had Pacific ridging moving toward BC and the PNW. If the ridge holds, the late-month wet signal is weaker. https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html - [2026-10-05] Sept was the coldest since 2007, yet a record-low 80 rainy days fell through Sept. Dry streaks can break quickly: KIRO says October "can change pretty quickly". The record Oct dry spell is 23 days (1986). The driest October was 0.31" in 1987. The wettest was over 10" in 2016. The 1987 and 2016 extremes show how wide the distribution is. https://www.kiro7.com/news/local/seattle-begins-october-with-dry-weather-following-an-unseasonably-cool-month/I4XGYWXMWJAAPH4OK76BDOT6SE/ - [2026-10-05] The Oct 6 AFD forecast only 0.1–0.25" for the Oct 9–10 system. Actual Sea-Tac rain was near 0.06" through Oct 13. Forecast systems in this pattern have underdelivered, which counts against YES. https://l-36.com/weather.php?lat=47.68&lon=-122.41&point1=Seattle%2C+WA&point2=Marine+Location+Near+Seattle%2C+WA - [2026-10-10] Weathertab, a low-skill proprietary long-range product, rates Oct 21–31 as having "fewer" dry days (higher rain risk). It rates early October as lower risk. This is weak support for a wet finish. https://www.weathertab.com/en/c/10/united-states/washington/seattle/ - [2026-10-07] Climate-data.org's climatology has the wettest 10-day block as Oct 21–31. A late-month wet finish is the normal seasonal ramp-up. Most remaining normal rain therefore falls after Oct 20, which is the window YES needs. https://en.climate-data.org/north-america/united-states-of-america/washington/seattle-593/t/october-10/ Path to YES: a 0.3–0.7" total from the Oct 17–20 systems, then a late-month atmospheric river or windstorm series (Oct 22–31) adding about 1.3–1.6". Prerequisites: the trough over the West Coast persists past Oct 21 (it is near-normal on CPC, not wet). The Pacific ridge does not park over BC. At least one multi-day system produces 1"+ at Sea-Tac. A single event of that size is plausible: the 2021 Oct 28 daily total was 1.99". BOTTOM LINE: The best YES case is an active trough pattern from Oct 17–20 (NWS AFD, CPC 6–10 day) followed by the climatologically wettest stretch, Oct 21–31. That still needs about 1.94" in 18 days, with CPC only near-normal for Oct 21–27 and recent forecasts having underdelivered. I found no sourced amount for Sea-Tac above about a quarter inch. NOT FOUND: Sea-Tac quantitative precipitation forecasts (WPC/NWS) for Oct 17–20 and later. CPC probabilities for Washington precipitation in Oct 21–27 beyond "near-normal". Any Oct 14 CLISEA update. A historical analogue of Octobers that were dry through Oct 13. Other venues' prices and sibling-strike prices (deliberately not searched).

YES means: official Sea-Tac (CLISEA) October 2026 total precipitation is strictly greater than 2.00". - [2026-10-13] The CPC 8–14 day discussion (issued Oct 13, valid Oct 21–27) puts Washington at "N" (near median) for precipitation. It says ridging over the Pacific moves toward BC and the Pacific Northwest. It says near-normal precipitation is favored along the Pacific Northwest coast "behind the mid-level trough axis". The wet signal sits in the Great Basin, Southwest and central US, not Puget Sound. The 6–10 day outlook (Oct 19–23) has troughing along the West Coast but only weak negative height anomalies. Near-median precipitation over a week normally means about 0.7–1.0" at Sea-Tac, not the 1.9" needed. https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html - [2026-10-13] FOX 13's Oct 13 forecast says Oct 14 rain will be under 0.25" and mostly on the coast and in the northwest interior. It describes Saturday Oct 17 as a frontal system with "a few shower chances", mainly on the coast and in the North Cascades. The Sunday–Monday (Oct 18–19) system brings "more showers and breezy winds". That is shower language, not atmospheric-river language. The near-term setup therefore adds perhaps 0.1–0.5" by Oct 19. https://fox13seattle.com/weather/seattle-weather-more-clouds-slight-chance-coast-sprinkles-tuesday - [2026-10-11] The NWS Seattle forecast discussion shows the Oct 13–14 atmospheric river aimed at Vancouver Island and central BC, not Puget Sound. It gave only a "slight chance" of rain along the coast and the Canadian border. The first dry-ridge/offshore-flow phase runs to Friday Oct 16. The first possible system is Friday night into Saturday. The first 16 days of October will probably end with under 0.3" total. https://a.atmos.washington.edu/data/disc_report.html - [2026-10-13] KIRO 7 expects the weekend and the following week to cool only to the low 60s and upper 50s, with the Wednesday rain north of Seattle. It describes the week as mainly dry. https://www.kiro7.com/weather/forecasts/drier-conditions-thursday/PX25E7IDLRAHJEMIPT6KLXWNME/ - [2026-10-13] The AccuWeather 10-day snapshot (undated, cached) shows low-probability, drizzle-type rain for Oct 17–22. This is weak evidence of a persistent wet regime. https://www.accuweather.com/en/us/seattle/98104/weather-forecast/351409 - [2026-10-06] Local media on Oct 6 noted a record-low 80 days of measurable rain through September, so the dry regime predates October. KIRO also noted the record October dry spell is 23 consecutive days (1986), and that the driest October is 0.31" (1987). That shows deep dry-start Octobers exist. https://www.kiro7.com/news/local/seattle-begins-october-with-dry-weather-following-an-unseasonably-cool-month/I4XGYWXMWJAAPH4OK76BDOT6SE/ - [2026-10-14] Reaching the line takes a heavy event. Sea-Tac's record single-day total is 5.02" (Oct 20, 2003), so one extreme storm could do it alone. Such storms are rare, and the CPC's Oct 13 week-2 outlook and the Oct 13 local forecasts show no flood, atmospheric-river or heavy-rain signal for Puget Sound through Oct 27. The CPC hazards outlook of Oct 13 lists heavy-precipitation risk only for the Southern Plains and Mississippi Valley. https://www.cpc.ncep.noaa.gov/products/predictions/threats/threats.php - [2026-10-14] Arithmetic for the No case: after about 0.3–0.5" by Oct 19, the remaining need is about 1.5–1.7" over Oct 20–31. The 1991–2020 normal for that span is roughly 1.8–2.0" (my estimate, not sourced). With CPC near-median odds for Oct 21–27, a below-normal El Niño lean, and the strongest-looking storm at Oct 18–19 only "breezy showers", the path to YES requires an above-normal final 10 days. Only the final week of the month, Oct 28–31, is beyond CPC range. - [2026-10-14] The Old Farmer's Almanac gives about 3" for the month, and "isolated showers" Oct 24–31. This is low-skill but not wetter than the dynamical outlooks above. https://www.almanac.com/weather/longrange/zipcode/98125 - [2026-10-14] Resolution technicality: the official figure is the final CLISEA/TWC daily climate report total. The market needs strictly more than 2.00", so exactly 2.00" resolves No, as does any small gauge-vs-other-station gap. Nearby non-airport stations (Seattle city, Boeing Field) can show more rain, and Sea-Tac is often drier. Rain amounts in forecasts for "Seattle" or the Puget Sound often overstate the Sea-Tac gauge. No rainfall after Oct 31 counts. BOTTOM LINE: Sea-Tac is almost 2" short with 18 days left, the CPC's Oct 21–27 outlook is near-median rather than wet for Washington, and the near-term systems are described as showers. A Yes would need an unforecast heavy-rain event, or an above-normal Oct 28–31, on top of an already dry El Niño-lean pattern. NOT FOUND: Quantitative NWS/WPC rainfall totals for Sea-Tac for Oct 16–19 or beyond. The CPC probability for the Oct 14–31 span at Sea-Tac. A dry-start-conditioned historical analogue. The Oct 14 CLISEA update. Ensemble (ECMWF/GEFS) Sea-Tac totals through Oct 31.