Will October be Melbourne's wettest month of 2026?

- [2026-10-18] The BoM Daily Weather Observations page for Melbourne (prepared 05:36 UTC, 18 Oct) shows a **66.2 mm** total for 1–18 Oct. That is already above August's 66.0 mm. Nearly all of it fell on 2–4 Oct: 48.4, 8.8 and 6.8 mm. https://www.bom.gov.au/climate/dwo/202610/html/IDCJDW3050.202610.shtml - [2026-10-18] The page's rainfall comes from Olympic Park (station 086338), the resolution station. A footnote says "Most observations from Olympic Park, but some from Melbourne Airport". The DWO total is a provisional daily product, not the Monthly rainfall table. https://www.bom.gov.au/climate/dwo/202610/html/IDCJDW3050.202610.shtml - [2026-10-18] The BoM Monthly rainfall table for 086338 has no October 2026 entry yet. It shows 2026 as: Jan 1.6, Feb 44.6, Mar 59.2, Apr 19.0, May 49.0, Jun 52.2, Jul 44.4, Aug 66.0, Sep 18.4. August is the highest so far. https://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=139&p_display_type=dataFile&p_stn_num=086338 - [2026-10-18] The same table lists a long-term (1961–1990) Oct mean of 64.2 mm and a Nov mean of 64.4 mm. The station's highest Nov total is 127.8 mm (2025) and its highest Oct total is 149.0 mm (2022). So Nov or Dec could still beat October if either is very wet. https://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=139&p_display_type=dataFile&p_stn_num=086338 - [2026-10-05 to 2026-10-17] Almost no rain after 4 Oct. Daily falls were 0 mm except 0.4 mm on 12 Oct and 1.6 mm on 13 Oct. Elders shows the same 66.2 mm total through 17 Oct. https://eldersweather.com.au/month-history/vic/melbourne - [2026-10-18] The forecast is dry and warm through about 23 Oct. Showers are likely around 23–26 Oct, so October should gain a little more rain. WillyWeather (18 Oct) gives 65% for 1–10 mm on 23 Oct and 75% for 5–15 mm on 24 Oct. The weather25 14-day outlook (19 Oct) sums to about 9 mm for the next 14 days, including 15.5 mm on 26 Oct. These are model outputs and vary by source. https://rainfall.willyweather.com.au/vic/melbourne/melbourne.html https://www.weather25.com/amp/oceania/australia/victoria/melbourne?page=14 - [2026-10-18] October is effectively no lower than 66.2 mm, because rainfall totals can only rise. It therefore looks set to finish above August's 66.0 mm unless the final published figure differs from the provisional DWO figure. Any later rain in the month only widens the lead. The first-published monthly figure in the Monthly rainfall table is what resolves the market. - [2026-08-27 to 2026-08-19] The BoM spring outlook (issued late Aug) has southern Victoria drier than average through spring. An El Niño is active and is expected to strengthen. Victorian agencies warned of a warm, dry spring (19 Aug). This points to a lower Nov/Dec rainfall tilt, but the outlook is probabilistic. https://pulse.auctionsplus.com.au/aplus-news/weather/boms-winter-rainfall-call-missed-what-spring-2026-has-in-store https://emergency.vic.gov.au/news-and-media/warm-and-dry-spring-ahead-potential-for-early-start-for-bushfire-danger-period - [2026-09 final] September was 18.4 mm, so it is not a contender. Same table as above. - Still to come before the market closes: the rest of October (13 days), then November and December. The October figure should appear in the BoM table in early November. The December figure is due about 1–8 Jan 2027. BOTTOM LINE: October already has 66.2 mm (provisional, to 18 Oct), which is above August's 66.0 mm, and the 23–26 Oct forecast points to more rain. So October is currently the leading month, and only a very wet November or December (or a lower final published figure) would displace it. The El Niño and dry-spring outlook lowers the odds of that. NOT FOUND: the official October entry in the BoM Monthly rainfall table (not yet published); an official BoM Melbourne point forecast with rainfall amounts (I used third-party forecasts); any November or December 2026 rainfall data (these months haven't happened yet).

- [2026-10-18] BOM daily observations for Olympic Park (086338) show October at **66.2 mm after 18 days**. That is already above August's 66.0 mm, the highest total so far in 2026. The page is provisional. 48.4 mm fell on 2 Oct and 8.8 mm on 3 Oct. Since 4 Oct, only about 8.8 mm has fallen (6.8 mm on 4 Oct, then 0.4 mm on 12 Oct and 1.6 mm on 13 Oct). https://www.bom.gov.au/climate/dwo/202610/html/IDCJDW3050.202610.shtml - [2026-10-18] The BOM forecast for the next week is light. Tue 20 and Wed 21 Oct have 40% chance of 0–2 mm. Fri 23 Oct has 90% chance of 2–15 mm with a possible thunderstorm. Sat 24 Oct has 50% chance of 0–5 mm. October therefore looks set to finish at or above 66.2 mm, probably around 70–85 mm. https://www.bom.gov.au/places/vic/east-melbourne/forecast/ - [2026-10-18] WillyWeather, which uses BOM probabilities, lists Fri 23 Oct at 65% for 1–10 mm and Sat 24 Oct at 75% for 5–15 mm. https://rainfall.willyweather.com.au/vic/melbourne/melbourne.html - [2026-10-17] ABC meteorologist Tom Saunders says October is "particularly damp" nationally, and modelling suggests at least some rain for Victoria over the next eight days. A high stalled in the Tasman Sea is feeding moisture. He says November is tipped wetter than normal across most of Australia, but modelling favours a drier month "along the coast from about Adelaide to Melbourne". https://www.abc.net.au/news/2026-10-17/2026-may-become-australias-wettest-el-nino-weather-year/107273884 - [2026-10-06] BOM weekly update: a low formed near the NSW–Victoria border on 2 Oct and gave persistent, widespread rain. Flood watches covered central and northern Victoria. https://www.beefcentral.com/weather/weekly-rainfall-update-rainfall-outlook-5-october-2026/ - [2026-09 summary] September 2026 at Olympic Park was 18.4 mm, 43% of its 42.7 mm long-term average. Winter 2026 was 162.6 mm, 130% of average. https://www.bom.gov.au/climate/current/month/vic/melbourne.shtml - [Base rate, long-term mean] The October long-term average is about 62–64 mm, from third-party climate sites. https://www.weather2travel.com/victoria/melbourne/october/ and https://en.climate-data.org/oceania/australia/victoria/melbourne-764100/t/october-10/ BOM's September average at this site is 42.7 mm. Annual rainfall is roughly 515–600 mm (Wikipedia gives 515.5 mm), so a typical month is around 45–55 mm and Melbourne's monthly rainfall is fairly flat across the year. A 2026 calendar-year peak of only 66.0 mm (August) is a low bar, and the October total is already above it. - [Base rate, past years] Olympic Park's wettest month varies by year. In 2022 it was October at 149.0 mm (https://www.bom.gov.au/climate/current/annual/vic/archive/2022.melbourne.shtml). In 2020 it was April at 138.4 mm (https://www.bom.gov.au/climate/current/annual/vic/archive/2020.melbourne.shtml). October 2021 was 110.4 mm, the highest October since 2010 (https://www.bom.gov.au/climate/current/month/vic/archive/202110.melbourne.shtml). I did not compile a full historical frequency of October being the wettest month. - [Reference class for Nov/Dec beating October] November's and December's long-term averages are roughly 55–60 mm (my general knowledge; I did not verify this from a fetched source). To beat an October of about 70–85 mm, either month would need an above-average, wet-tail month. The BOM/ABC outlook for the Melbourne coast in November leans dry, which is a mild headwind for that route. - [2026-08] The BOM outlook issued about late July said August–October rainfall was likely below average for most eastern states. https://www.beefcentral.com/weather/aug-oct-2026-rainfall-outlook/ The actual October to date is wet, so that outlook is not holding for this month. - [2026-10-18] Extra context: 2026 is a strong El Niño year yet unusually wet nationally. ABC says none of the 27 previous El Niño years since 1900 had above-average winter–spring rain. This adds uncertainty to any November or December dryness assumption. https://www.abc.net.au/news/2026-10-17/2026-may-become-australias-wettest-el-nino-weather-year/107273884 BOTTOM LINE: October is already the wettest month of 2026 on provisional data (66.2 mm against August's 66.0 mm), with 13 days still to run and showers forecast for 20–24 Oct. The remaining uncertainty is mainly whether November or December exceeds October's final total, which would need roughly 70–90+ mm. That is above-average for either month, and the November outlook for the Melbourne coast leans dry. NOT FOUND: A computed historical frequency of October being Melbourne's wettest month. BOM's long-term November and December averages for Olympic Park. A BOM December outlook. Any other Polymarket or other venue's contracts for this event.

YES means: October 2026 is Melbourne (Olympic Park, 086338) calendar month with the highest total of 2026. That needs October's first-published total to beat August's 66.0 mm and also to beat or tie November and December. - [2026-10-18] The BoM DWO page for 086338 (prepared 05:36 UTC 18 Oct, fetched) shows 66.2 mm for 1–18 Oct. 18 Oct is a dry 0 mm day in the table. October already leads August by 0.2 mm, and the daily-total gap is thin. The 1 Oct entry is 0.2 mm and 2 Oct is 48.4 mm, so 2 Oct alone is 73% of the total. https://www.bom.gov.au/climate/dwo/202610/html/IDCJDW3050.202610.shtml - [2026-10-19] The newer BoM point forecast (issued 04:05 AEDT 19 Oct; East Melbourne) gives rain amounts above the earlier reports' figures. Sat 24 Oct has 80% chance, 1–20 mm. Sun 25 Oct has 90% chance, 2–25 mm. A thunderstorm is possible both days. Tue 20 to Fri 23 Oct total 0–2 mm. The 24–25 Oct range alone is 3–45 mm, so October looks likely to end well above 66.2 mm. https://www.bom.gov.au/places/vic/east-melbourne/forecast/ - [2026-10-19] Mechanism for a buffer over the 0.2 mm lead: a front from 24 Oct, preceded by hot northerlies (27–31 °C forecast for 20–23 Oct). October could finish near 70–95 mm if the BoM ranges hold. That would need November or December to reach about that level. Based on the BoM forecast ranges. https://www.bom.gov.au/places/vic/east-melbourne/forecast/ - [2026-10-15] The BoM climate outlook (issued 15 Oct) gives a 60–80% chance of below-average Nov–Jan rainfall for southern Victoria. It says a strong El Niño is underway and is likely to peak around Nov–Dec as a very strong event. This is a newer and firmer dry tilt than the late-Aug spring outlook. https://www.bom.gov.au/climate/ahead/outlooks/ - [2026-10-15] The same outlook notes a strong El Niño does not necessarily mean strong impacts on Australian rainfall. It is a probabilistic tilt, not a guarantee. https://www.bom.gov.au/climate/ahead/outlooks/ - [2025-11 / 2022-11 / 2024-11] BoM Olympic Park November totals show the November bar: long-term average 59.1 mm. Nov 2025 was 127.8 mm (216%). Nov 2022 was 73.8 mm. Nov 2024 was 63.4 mm. Nov 2023 was 42.4 mm. Nov 2018 was 97.8 mm. So reaching about 70–95 mm is a roughly one-in-three-or-fewer event in the sampled years: 3 of 8 sampled Novembers exceeded about 70 mm (2025, 2022, 2018), and a fourth (2024) was near it. https://www.bom.gov.au/climate/current/month/vic/archive/202511.melbourne.shtml https://www.bom.gov.au/climate/current/month/vic/archive/202211.melbourne.shtml - [2026-10-18] Elders' history gives an Oct 1855–2025 average of 65.7 mm for Melbourne. October 2026 already matches that at 66.2 mm with 13 days to go, so a typical final-fortnight addition puts it above average. A November or December that beats a stronger October therefore needs an above-average month. https://eldersweather.com.au/month-history/vic/melbourne - [2026-10-18] A cross-check gauge: WillyWeather's Essendon Airport total for October is 58.8 mm through 18 Oct, so the Olympic Park figure is not an outlier. That matters because the DWO page says some observations come from Melbourne Airport. https://rainfall.willyweather.com.au/vic/melbourne/melbourne.html - [2026-10-15] Climate-data.org lists a Melbourne mean December of 62 mm and Nov of 65 mm. Third-party averages put both months roughly level with October's norm, not above it. https://en.climate-data.org/oceania/australia/victoria/melbourne-764100/t/october-10/ - [2026-10-18] Single most likely path to YES: the DWO figure carries into the Monthly table at 66.2 mm or more (the table's 1 Oct–31 Oct sum). The 24–25 Oct front then adds the BoM-forecast 3–45 mm. November and December each finish below that total under the below-average outlook, with neither being a very wet month like Nov 2025. Prerequisites: (1) no downward revision between the DWO and the first-published table; (2) October closes above 66.0 mm; (3) November and December each stay below October's final total. BOTTOM LINE: October already leads August by 0.2 mm, and the BoM forecast of 3–45 mm on 24–25 Oct should widen that gap. The 15 Oct BoM outlook for a drier-than-average Nov–Jan in southern Victoria favours October holding the lead. The remaining risk is a wet November or December, as in Nov 2025 at 127.8 mm. NOT FOUND: The official October entry in the BoM Monthly rainfall table (not yet published). A BoM Dec-only outlook for Melbourne. The DWO-to-Monthly-table revision history for Olympic Park. Any other venue's market for this event.

YES means: October 2026 has the highest total of any calendar month of 2026 at Melbourne (Olympic Park, 086338), on first-published figures. A tie resolves to the earliest tied month. - [2026-10-18] The only route to NO is that November or December finishes above October's final published total. The 15 Oct BoM outlook cuts against that. It gives a 60–80% chance of below-average Nov–Jan rainfall for southern Victoria. The same page says a strong El Niño will probably peak in Nov–Dec as a very strong event. BoM adds that ENSO alone doesn't guarantee impacts on Australian rain. https://www.bom.gov.au/climate/ahead/outlooks/ - [2026-10-18] The same BoM page names a counter-signal. Sea surface temperatures around Australia's south-east are up to 3°C above average, and BoM says warm waters can raise the potential for high-intensity rain. A positive Indian Ocean Dipole is also expected to develop. Both are mild upside risks to a very wet Nov or Dec. https://www.bom.gov.au/climate/ahead/outlooks/ - [2026-10-15, as quoted by the Vic water snapshot] The Vic water snapshot reports 40–55% chance of exceeding median Nov–Jan rainfall across most of Victoria outside the south-west. That is near-neutral, not strongly dry. A NO case therefore can't lean on a firm dry signal for Melbourne. https://www.water.vic.gov.au/our-programs/water-monitoring-and-reporting/current-water-snapshot - [2026-10-18] Precision risk: the DWO sheet puts the margin over August at only 0.2 mm (66.2 v 66.0) before any further rain. The 1–18 Oct sum includes 0.2 mm on 1 Oct and 48.4 mm on 2 Oct. Media reported 47.8 mm to 3 pm on 2 Oct, a cut-off effect. DWO is provisional and the Monthly rainfall table could differ by a few tenths. The data show no rain on 14–18 Oct, and the page's own footnote says some observations come from Melbourne Airport. This is a thin NO path that further rain would erase. https://www.bom.gov.au/climate/dwo/202610/html/IDCJDW3050.202610.shtml - [2026-10-18] Rain after 4 Oct has been near zero. After 13 Oct, five straight days were 0 mm, and the 18 Oct entry is a part-day reading. October's total depends on one event, 2–4 Oct, which supplied 64.0 of the 66.2 mm. If the 23–24 Oct showers fizzle, October stays near 66–67 mm. That is the weakest case for YES, and a normal November would then be about as wet. https://www.bom.gov.au/climate/dwo/202610/html/IDCJDW3050.202610.shtml - [2026-10-02] Weatherzone said October averages 65.7 mm. The 48.4 mm on 2 Oct was already 74% of that. Weatherzone adds that October is typically Melbourne's wettest month. October is therefore the usual leader and a high-variance one. If the 2 Oct event is a one-off, the rest of October could be dry. https://www.weatherzone.com/au/news/heaviest-melbourne-rain-in-30-months-as-vic-flood-threat-increases/1891586 - [2026-10-18] BoM's Melbourne Airport statistics (not the resolution station) give a Nov mean of 62.4 mm. That is above the airport's Oct mean of 55.7 mm. Dec is 51.0 mm. At Olympic Park, the Nov mean is about 58.7–60.3 mm (BoM monthly summaries for Nov 2023 and 2022). November is not systematically drier than October at the airport, so the long-term averages offer no structural edge to October. https://www.bom.gov.au/climate/averages/tables/cw_086282.shtml - [2022–2025 archive] Wet Novembers and Decembers at Olympic Park have beaten Oct-sized totals before. Nov 2018 was 97.8 mm, Dec 2018 was 104.8 mm, and Nov 2021 was 96.6 mm. Nov 2022 was 73.8 mm, and the sibling report gives Nov 2025 at 127.8 mm. Any such month would exceed a likely October of about 70–85 mm. https://www.bom.gov.au/climate/current/month/vic/archive/201812.melbourne.shtml https://www.bom.gov.au/climate/current/month/vic/archive/202111.melbourne.shtml - [2026-10-18] Counter-examples show dry spells are common. Nov 2023 was 42.4 mm (72% of average), Dec 2024 was 38.6 mm, Dec 2019 was 6.2 mm, and Nov 2017 was 46.0 mm. A NO result needs a month in the top tail, not a typical one. This supports the "status quo = October wins" view and limits how strong a NO case can be. https://www.bom.gov.au/climate/current/month/vic/archive/202311.melbourne.shtml https://www.bom.gov.au/climate/current/month/vic/archive/201912.melbourne.shtml - [2026-10-17] Reported by BoM and Weatherzone, 2026 has been "wetter than normal" for non-Melbourne regions. The ABC piece (colleague-cited) says Nov is tipped wet nationally but dry along the Adelaide–Melbourne coast. Nov rain is a lottery driven by one or two cold-front or trough events, as Nov 2021 (45.4 mm of 96.6 mm on one day) and Dec 2018 (41.2 mm on one day) show. A single event of about 50 mm plus normal rain would beat 70–85 mm. https://www.bom.gov.au/climate/current/month/vic/archive/202111.melbourne.shtml - [Resolution mechanics] If Dec's figure isn't published by the deadline, Dec resolves No, so Dec can't win by default. Oct, Nov and Dec are each resolved on first-published figures. Revisions don't count, so a later correction can't help NO. A tie with August is impossible once October's total passes 66.0 mm. BOTTOM LINE: The strongest NO case is narrow. It needs a single big Nov or Dec event (about 70–90+ mm), or a first-published October figure that falls near August's 66.0 mm because the late-October showers fail. The BoM outlook (60–80% chance of below-average Nov–Jan rain for southern Victoria) leans against that. I found no source putting Nov or Dec on track to exceed October. NOT FOUND: the official October entry in the Monthly rainfall table, an official Olympic Park Nov or Dec mean from the table itself, and any forecast of a specific heavy event in Nov or Dec. I also found no historical frequency of Nov or Dec exceeding October at Olympic Park.