How much will it rain in Napa in November 2026 through March 2027? — Above 20 inches

- [2026-09-28] NOAA CPC's latest ENSO update confirms an El Niño Advisory is in effect, stating "El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter 2026-27." The latest weekly Niño‑3.4 anomaly was 2.2°C. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf - [2026-09-10] CPC's probabilistic ENSO outlook projects El Niño to persist through at least March–May 2027, i.e., for essentially the entire Nov 2026–Mar 2027 contract window, with only a possible transition to neutral starting April–June 2027. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf - [2026-09-17] CPC's official seasonal precipitation outlook (issued Sept 17, 2026, valid DJF 2026‑27) favors above‑normal precipitation across much of California, with coastal odds of above-normal precipitation reportedly reaching 50‑60% in the DJF/JFM/FMA windows according to secondary summaries of that map; the El Niño wet signal is described as strengthening through winter and peaking in January–March 2027. https://stormbag.co/blogs/news/noaas-new-winter-outlook-el-ninos-rain-arrives-late-hits-california-and-the-southeast-hardest - [2026-09-17] A separate summary of the same CPC map notes the signal is strongest and most reliable for Southern/Central California, while for the Bay Area/Sacramento Valley "a very strong El Niño tilts the odds toward a wet winter... but it does not guarantee one," i.e., confidence for Napa specifically is only medium. https://www.napavalley.com/weather/ (regional context) and https://stormbag.co/pages/el-nino-california-2026-27 - [2026-09-28] CFS.v2 model ensemble (NCEP, issued Sept 28, 2026) shows Niño‑3.4 anomalies remaining strongly positive through winter 2026‑27 before gradually declining into spring 2027, consistent with El Niño persisting across the full Nov–Mar window. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf - [2026-09-26] CPC's U.S. 30‑day precipitation‑departure map (through Sept 26, 2026) shows near/below‑normal precipitation over coastal/Northern California for the prior month, consistent with the normal dry late‑summer pattern; no rain has started the wet season yet. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf - [2026-10-02] to [2026-10-04] Weather Underground station data for KAPC (Napa County Airport) show 0.00 inches of rainfall recorded on Oct 2, 3, and 4, 2026, with hot, dry, clear conditions (highs in the 90s‑100s°F) — the contract's Nov‑Mar window has not yet begun and the preceding weeks remain dry. https://www.wunderground.com/severe/us/ca/napa/94581 ; https://www.wunderground.com/weather/us/ca/napa/94558 - [2026-10-04] NWS point forecast for KAPC shows continuing hot, dry, mostly clear conditions through at least Oct 11, 2026, with no rain chances in the near‑term 7‑day outlook. https://forecast.weather.gov/MapClick.php?lon=-122.29&lat=38.29 - [undated, 1991–2020 NOAA normals] KAPC's climatological average precipitation for Nov+Dec+Jan+Feb+Mar is approximately 2.18+4.33+4.37+4.02+3.19 ≈ 18.1 inches — meaning the 20‑inch threshold requires an above‑normal wet season (roughly 10%+ above the 1991‑2020 average for this five‑month span). https://www.extremeweatherwatch.com/cities/napa/average-rainfall-by-month - [through 2026-04-21] Napa's prior rain year (2025‑26, a weak La Niña year) was well below normal: year "2026," rank "123," precipitation "8.3" inches year-to-date through April 21, 2026 , and full calendar-year 2025 totaled only 15.8 inches (rank 103 of 126 years) — illustrating how a non‑El Niño year recently fell far short of 20 inches even over a full year. https://www.extremeweatherwatch.com/cities/napa/most-yearly-precipitation - [historical range] Napa's yearly precipitation records (1901‑2026) show wide variability, from extremes like 51.2 inches (1983) to lows near 4‑8 inches, but the most precipitation Napa has ever received in a single calendar year is 51.2 inches (1983) , and many strong El Niño years historically have produced well above 20 inches over Nov‑Mar specifically. https://www.extremeweatherwatch.com/cities/napa/most-yearly-precipitation - [2026-10-05] No rain has fallen yet in the contract period (which starts Nov 1, 2026); as of question-open date the entire Nov–Mar total is still 0.0 inches, and the first meaningful storm is not expected until at least mid-to-late October 2026 per long-range outlooks, with the wet season proper not beginning until November. https://www.wunderground.com/severe/us/ca/napa/94581 BOTTOM LINE: A historically strong, "very strong/possibly record" El Niño is firmly in place and forecast by CPC to persist through the entire Nov 2026–Mar 2027 window, with CPC's official seasonal outlooks tilting odds toward above‑normal precipitation for coastal/Northern California (confidence higher for Southern California, only medium for the Napa/Bay Area). Since Napa's 1991‑2020 Nov–Mar normal (~18 inches) sits just below the 20‑inch strike, an El Niño-driven wet bias meaningfully raises the chance of crossing 20 inches, but no rain has fallen yet and last year's (La Niña) season was far drier, underscoring that NorCal outcomes under El Niño remain uncertain rather than guaranteed. NOT FOUND: An official NWS/CPC Nov‑Mar seasonal precipitation outlook has not yet been issued specifically for that exact 5‑month window (seasonal outlooks are issued as overlapping 3‑month periods); I could not find The Weather Company's own KAPC historical Nov‑Mar sums for recent El Niño years (e.g., 2015‑16, 2023‑24) to benchmark directly against the 20‑inch strike, nor any CNRFC/NWS Sacramento Napa-specific water-year outlook issued in the last 30 days.

- [2026-10-05] Long-term climatology for Napa County Airport (KAPC) station, 1991–2020 NOAA normals, puts average monthly precipitation at roughly Nov 2.18", Dec 4.33", Jan 4.37", Feb 4.02", Mar 3.19" — summing to about 18.1" for the Nov–Mar window, i.e. January: 4.37 in; February: 4.02 in; March: 3.19 in; November: 2.18 in; December: 4.33 in , below the 20" threshold on average. https://www.extremeweatherwatch.com/cities/napa/average-rainfall-by-month - [2026-10-05] A separate Napa County Airport normal (1992–2021) lists very similar monthly values (Nov 2.19", Mar 2.88"), reinforcing that the climatological Nov–Mar mean sits in the high-teens, not clearly above 20". November Climate & Weather Averages in Napa: Precipitation 2.19". Annual precip.: 22.14" (per year) . https://www.timeanddate.com/weather/usa/napa/climate - [2026-10-05] Napa County Airport's official flight-planning page states Average rainfall is 23.88 inches in Napa with the majority occurring from November through March , implying the Nov–Mar share of the ~24" annual average is likely close to but not reliably over 20" in a typical year. https://www.napacounty.gov/1012/Flight-Planning - [2026-10-05] Base-rate variance is large: at nearby long-term gauges, Napa County RCD reports water-year (not quite Nov–Mar, but overlapping) totals ranging widely year to year — e.g. a below-normal year (WY2025-26) reaching only ~80% of mean annual precipitation by season's end, versus wetter years reaching 90%+ of average by February. Annual rainfall totals for Water Year 2025-26 to date range from 22.7 inches in the City of Napa to 39.7 inches at the top of Mt. St. Helena. These totals represent approximately 80% of our mean annual precipitation, indicating that this has been a below average water year. https://naparcd.org/water-year-2025-26-rainfall-summary-for-napa-valley/ - [2026-10-05] In a strong El Niño comparison year (2015-16), by end of January the Napa Valley had only reached 57-59% of its annual average rainfall, showing that even strong El Niño years can still be running below pace mid-winter before late-season storms arrive. As of the end of January, Napa Valley has received 57% of our annual rainfall which has almost caught us up and put us on track for an average year. Mean annual precipitation for Mount Saint Helena is 48.44 inches, which means we have received 66% of the annual average as of the end of this January. In the City of Napa, mean annual precipitation is 25.22 inches and we have received 59% of the annual average so far. https://naparcd.org/how-does-this-years-rain-compare-to-normal/ - [2026-10-05] Current ENSO state is a very strong, "historic" El Niño: During the October-December 2026 season, there is a 75% chance of a historic event that would exceed the strength of previous El Niño events dating back to 1950. In summary, El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter 2026-27. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml - [2026-09-17] NOAA's official seasonal outlook favors wetter-than-normal conditions for California this winter: The updated NOAA Climate Prediction Center outlook favors above-normal precipitation across much of the southern United States, including California, the Southwest, southern Rockies and Southeast... Above-normal precipitation is favored across California, Arizona, New Mexico, much of Texas and portions of the southern Rockies. https://unofficialnetworks.com/2026/09/17/noaa-cpc-updated-winter-outlook/ - [2026-08-20] NOAA's outlook specifically signals the wet signal arrives late, peaking Jan–Mar 2027, and raises above-50% odds of above-normal precip for coastal California, with 1998 (a historic strong El Niño) cited as an analog for a very wet February: Forecasters write that El Niño impacts are expected to increase "slowly at first before quickly ramping up during the core winter months and especially late winter." The outlook says January through March 2027 is when coverage peaks. https://stormbag.co/blogs/news/noaas-new-winter-outlook-el-ninos-rain-arrives-late-hits-california-and-the-southeast-hardest - [2026-09-30] However, the El Niño–Northern California rainfall relationship is historically mixed, not a reliable predictor of a wet Napa winter: NWS Sacramento's September briefing leans toward above-normal precipitation for the coming winter, but says El Niño's historical rainfall relationship there has been mixed. In the six very strong events shown in its briefing, Northern California had two wet winters, two near-normal winters and two dry winters. This is a direct caveat for Napa, which sits in the North Bay/Northern California climate division. https://stormbag.co/blogs/stormbag-flood-protection-blog/super-el-nino-2026-27-what-noaas-off-the-charts-forecast-means-for-the-year-ahead - [2026-10-05] Interannual variability is extreme: historical records show the driest Novembers at Napa County Airport near-zero and the wettest Novembers over 9" (250mm ≈ 9.8"), illustrating that any single Nov–Mar season outcome can deviate very far from the ~18" average in either direction. The wettest November on record was 1983 with 250 mm, while the driest was 1995 at 5 mm. https://weatherblaze.com/weather-history/us/california/napa/november/ - [2026-10-05] Statewide seasonal rainfall archives (Golden Gate Weather Services) confirm that Northern/Central California seasonal totals swing widely year to year as percentages of normal (seen e.g. in recent-season tables showing totals from under 50% to over 170% of normal at various stations), underscoring that "above normal" seasonal outlooks do not guarantee any specific numeric threshold is cleared. https://ggweather.com/ca2022rain.htm NOT FOUND: A complete year-by-year historical series of Nov 1–Mar 31 cumulative totals specifically at KAPC (to compute an empirical historical "% of years above 20 inches" base rate) was not located; only monthly climatological normals and scattered season summaries were available. Also could not find any existing betting/forecast market history or track record for this specific Kalshi contract or prior-year analogs of it. BOTTOM LINE: The long-run Nov–Mar climatological average at Napa is roughly 18–19 inches, just under the 20-inch threshold, meaning a purely average season would resolve "No"; but this year's forecast "historic" strong El Niño and NOAA's above-normal precipitation outlook for California (peaking Jan–Mar 2027) tilt the odds toward a wetter-than-average season, tempered by NWS Sacramento's own caveat that Northern California's response to very strong El Niño winters has historically been a coin-flip (2 wet / 2 near-normal / 2 dry in six past events).

YES means: cumulative Weather Company daily precipitation at KAPC for Nov 1, 2026–Mar 31, 2027 sums to strictly more than 20.00 inches. - [2026-10-05] Golden Gate Weather Services' Jan Null climatology dataset (based on 1981‑2010 normals) shows that for the "SF Bay" hydrologic region — Napa's region — the average of the three historical Very Strong El Niño seasons (1982‑83, 1997‑98, 2015‑16) was 152% of normal seasonal precipitation, far above the ~110% of normal needed to clear the 20‑inch strike given the ~18.1" Nov‑Mar climatological baseline. https://www.ggweather.com/ca_enso/ca_elnino.html - [2026-10-05] Individually, two of the three Very Strong El Niño years far exceeded the 110%-of-normal bar for SF Bay: 1982-1983 155% 163% 159% 187% (N Coast/Sacramento/N Lahontan/SF Bay) and 1997-1998 145% 158% 128% 173% , with only 2015-16 falling short at 95% for SF Bay — i.e. a 2-of-3 historical hit rate for this exact ENSO category. https://www.ggweather.com/ca_enso/ca_elnino.html - [2026-09-04] The Napa Valley Register (published Sept 4, 2026) directly quantifies the two strongest historical analogs in Napa terms: Strong El Niño conditions were present in such drenching rainfall years as 1982-83, when Napa State Hospital received a record 50.19 inches, and 1997-98, when it received 42.75 inches. Both are more than double the 20-inch strike even as full-year totals, not just Nov–Mar. https://napavalleyregister.com/news/local/weather/napa-rain-weather-wine-el-nino-storms/article_074a217e-6131-11ee-9fa3-439d51f1636f.html - [2026-09-15] A more recent Napa Valley Register piece (published Sept 4, 2026 per article metadata) reiterates that the record-setting analog remains directly relevant for this year's "Super El Niño": The 1997-98 super El Niño resulted in more than 42 inches of rain falling at Napa State Hospital. https://napavalleyregister.com/news/napa-county-wine-weather-rain-super-el-ni-o-floods-thomasser/article_ee55c422-402b-4038-b69e-21afe1d3ebf3.html - [2026-09-05] NOAA's NCEI historical county precipitation dataset confirms Napa County's Dec 1982–Apr 1983 cumulative total reached 45.15 inches (198% of normal for that span), directly corroborating the Register's station-level 1982‑83 figure and showing the wet season delivered its bulk well before April. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/county/mapping/4-pcp-198304-5.xml - [2026-09-04] The same article frames current conditions as a repeat of that setup: a 75% chance the 2026‑27 event "would exceed the strength of previous El Niño events dating back to 1950," meaning this year's event could rank at or above 1982‑83 and 1997‑98 in strength — both of which are the two analogs that blew through the 20‑inch threshold. (Context echoed in the stormbag.co summary: to a very strong El Nino for the 2026-27 Northern Hemisphere winter, and a 69% probability that the event will surpass every El Nino on record since 1950. For California, that translates into above-normal precipitation probabilities exceeding normal thresholds.) https://stormbag.co/pages/el-nino-california-2026-27 - [2026-09-04 article, referencing Sept 2026 analog framing] Forecasters cited in the same Register piece explicitly identify this winter's closest historical analogs as the 1997‑98 and a more recent 2024 winter, both "record-breaking" for California: The forecast's closest historical analogs are the 1997-98 winter and the 2024 winter. Both produced record-breaking precipitation across parts of California, and both ranked among the wettest Februaries in the last 100 years for portions of the state. https://stormbag.co/pages/el-nino-california-2026-27 - [2026-09-04] The Register article also notes the mechanism by which very strong El Niño delivers Napa's biggest totals: storms concentrate heavily in the back half of the season. A sister Register article from the 2015‑16 cycle quotes a NWS Monterey hydrologist: forecasters said the bulk of El Niño -related rains have come down after New Year's Day during past occurrences, with storms picking up in strength and frequency in January of 1983 and 1998. "What we saw in '97 and '82 was a majority of the rainfall falling after Jan. 1, or at some point in December," — meaning a slow start to the Nov‑Dec portion of the contract window would not preclude a late-season surge past 20 inches, consistent with CPC's own Jan‑Mar peak timing noted by colleagues. https://napavalleyregister.com/news/local/napa-rainfall-lags-behind-past-el-ni-o-years-so-far/article_8d9ef4fe-af1c-53cd-92ac-8e06c3bae5cd.html - [2026-09-04] This mechanism matters for the strike specifically because the Nov‑Mar window captures the full December–March core when historical Very Strong events deliver their biggest monthly totals, rather than cutting off before the peak — unlike water-year-to-date snapshots taken in early winter that understate eventual seasonal totals. BOTTOM LINE: The two strongest historical analogs for a "very strong/potentially record" El Niño at Napa's own stations — 1982‑83 (SF Bay region 187% of normal) and 1997‑98 (SF Bay 173% of normal) — both landed far above the ~110%-of-normal level needed to clear 20 inches over Nov‑Mar, giving a 2‑of‑3 historical hit rate for this ENSO category and a regional average of 152% of normal; if 2026‑27 behaves like either of those two rather than the drier 2015‑16 outlier, the 20‑inch threshold would be cleared comfortably, often by a wide margin. NOT FOUND: An exact Nov 1–Mar 31 (as opposed to calendar-year, water-year, or Dec‑Apr) cumulative figure specifically for KAPC in 1982‑83 or 1997‑98 was not located, nor a station-level SF Bay/Napa-specific percent-of-normal table confirming whether 2015‑16's shortfall (95%) was driven by a wet Dec‑Jan but dry Feb‑Mar or vice versa.

YES means: The Weather Company's summed daily precipitation at KAPC for Nov 1, 2026–Mar 31, 2027 comes in strictly above 20.00 inches. This dimension argues for NO (20 inches or less). - [2026-09-24] NWS Sacramento's own seasonal briefing — the agency with direct forecast authority over Napa — concedes El Niño's rainfall relationship for Northern California is unreliable: "NWS Sacramento's September briefing leans toward above-normal precipitation for the coming winter, but says El Niño's historical rainfall relationship there has been mixed. In the six very strong events shown in its briefing, Northern California had two wet winters, two near-normal winters and two dry winters." That is a 33% historical hit-rate for "wet," not a strong tilt toward crossing a stretch threshold like 20 inches. - [2026-09-24] NWS Sacramento's briefing explicitly warns against extrapolating from El Niño strength to actual outcomes: "Record Strength does not guarantee Record Impacts." The same source cautions that seasonal guidance "cannot reliably specify how many storms a community will get, how strong they will be, whether they will arrive in a damaging sequence." - [undated/compiled ~2026-09-30] The most directly comparable recent "super El Niño," 2015-16 — then the strongest ENSO event on record — produced a well-below-threshold outcome for this exact region: "The 2015-16 event famously disappointed the Bay Area and points north despite being the strongest event on the raw index since 1950... A very strong El Nino tilts the odds toward a wet winter for the Bay Area and Sacramento Valley, but it does not guarantee one." - [2026-09-04] A Napa-specific retrospective confirms the 2015-16 bust in hard numbers: despite official predictions of "30 inches of rain or more," "weather officials for 2015-16 predicted a super El Niño and lots of rain for California. Napa State Hospital received about 18 inches." Since roughly 70-75% of Napa's annual total normally falls in the Nov–Mar core (per the ~18.1" Nov-Mar vs ~24-25" annual normal cited in prior reports), an ~18" full-year total implies a Nov-Mar sum well under 20 inches in that marquee El Niño year. - [2026-09-04] The very next hyped El Niño season also missed its own forecast: the same article notes forecasters predicted 2023-24 would bring 30+ inches, but a companion 2026 retrospective states "the 2015-16 and 2023-24 super El Niño rain years delivered average rainfall" rather than the forecast surplus — a second consecutive bust of "super El Niño = big rain" framing for Napa specifically. - [2026-09-04] For contrast, the non-El Niño 2022-23 season (not an El Niño analog) delivered the truly exceptional total cited in the same piece — "a non-El Niño year when more than 32.5 inches fell at Napa State Hospital" — showing that Napa's biggest wet years in the past decade have come from atmospheric-river-driven non-ENSO winters, not from El Niño itself, undercutting the mechanism this market is pricing. - [2026-09-30] Even the bullish seasonal outlook sources concede Northern California's signal is secondary to Southern California's: "Northern California is a different story. The signal there is weaker and less consistent." - [2026-08-20] The CPC's own winter outlook (Aug 20 issuance) places the wet signal's peak later in the window and frames it as a probabilistic lean rather than a lock: "NOAA's August 20 seasonal outlook favors above-normal rain for the Southeast and coastal California, peaking January-March 2027." A late-arriving, back-loaded signal raises the chance that a dry Nov-Dec start (consistent with the still-dry conditions noted in other reports) is never fully offset within the Jan-Mar window. - [1901-2026 calendar-year series] Of the 20 calendar years from 2006-2025, annual totals exceeded roughly 27-28" (a level that would comfortably support >20" in the Nov-Mar core alone) in only about 6 of those 20 years, per the full ranked table "| 2024 | 49 | 24.2 |\n| 2023 | 38 | 27.3 |\n| 2022 | 114 | 11.9 |\n| 2021 | 72 | 20.5 |\n| 2020 | 125 | 5.9 |\n| 2019 | 33 | 28.4 |\n| 2018 | 100 | 16.6 |" — confirming that even in a typical 20-year sample, "clearly above 20 inches in the wet core alone" years are a minority, not the base case. - [2026 water year] The most recent completed water year (2025-26, Oct 2025–Sep 2026), not an El Niño year, closed only modestly below average — NWS data showing "Napa State Hospital has had 21.59 inches, a few inches below normal. However, this site on some days doesn't report data, which can lead to lower-than-actual totals. AccuWeather reported 22.69 inches falling there as of late August." — for the full 12-month year, reinforcing that hitting 20"+ in just the 5-month Nov-Mar core requires meaningfully above-normal performance, not merely an average year. BOTTOM LINE: Napa's own two most recent "super El Niño" seasons (2015-16 and 2023-24) both underperformed their hyped forecasts and delivered only average-to-below-average rainfall, and NWS Sacramento's own historical sample for very strong El Niño events in Northern California is a split 2-wet/2-normal/2-dry record with explicit warnings that "record strength does not guarantee record impacts" — giving a credible, evidence-based path to a sub-20-inch Nov-Mar outcome despite the current El Niño's strength. NOT FOUND: An exact Nov 1–Mar 31 (as opposed to full water-year or calendar-year) historical total for Napa State Hospital/KAPC in the 2015-16 or 2023-24 seasons; precise monthly breakdowns confirming how much of the ~18" (2015-16) or ~32.5"/average (2023-24) totals fell specifically within the Nov-Mar window versus April-October.