Will Madison fall below 30°F from issuance through Oct 31, 2026?

- [2026-10-17] KMSN obs so far, from the NWS 3-day history. Temperatures fell overnight: 36°F at 00:53 CDT, 34°F at 01:53, 32°F at 02:53 and 30.9°F at 03:53. The latest observation I could see was 11:20 UTC (6:20 CDT), at about -1°C (≈30°F; the API rounds to whole °C). Sunrise is about 07:12 CDT, so the low may not be in yet. These are NWS ASOS readings, not the TWC hourly feed that resolves the contract. I could not see any reading strictly below 30°F. Overnight and early-morning readings (the 04:53–07:53 CDT hourly observations) are the key unknown. https://forecast.weather.gov/data/obhistory/KMSN.html - [2026-10-17] KMSN's latest API observation (11:20 UTC) shows clear sky and calm wind, with a "V" (validated) quality flag. https://api.weather.gov/stations/KMSN/observations/latest - [2026-10-16] NWS Madison forecast put the Oct 16–17 overnight low at about 31°F, with widespread frost after 3–4 am. A Freeze Warning ran 1–9 am CDT Saturday Oct 17. https://forecast.weather.gov/MapClick.php?lat=43.07313000000005&lon=-89.38643999999994 - [2026-10-16] WMTV said temperatures would fall to the upper 20s to around 30°F for most areas, with mid-20s possible farther northwest, and called it the first widespread freeze of the season. https://www.wmtv15news.com/2026/10/16/first-freeze-tonight-then-big-warmup/ - [2026-10-16] Channel3000 had the freeze warning at "as low as 28" for south-central Wisconsin. WKOW's forecast low was 31°F. https://www.channel3000.com/weather/forecast/ - [2026-10-16] Forecast after the freeze: Saturday high is mid-to-upper 50s and Saturday night low is about 39°F. Sunday is in the low 60s, Monday has a high near 65 and a low near 43, and Tuesday's high is near 69. Wednesday may approach 70. https://forecast.weather.gov/MapClick.php?site=MKX&map.x=159&map.y=151 - [2026-10-16] The CPC 6–10 day outlook (Oct 22–26) strongly favors above-normal temperatures east of the Rockies, with probabilities above 80% over parts of the Upper Midwest. https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html - [2026-10-16] The CPC 8–14 day outlook (Oct 24–30) shows Wisconsin above normal for temperature. It keeps ridging over the eastern US longer into week 2 than the previous day's outlook did. https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html - [2026-10-14/15] Before the cold snap it was mild. KMSN was 62°F on the 14th and 54–57°F on the 15th, with rain. https://forecast.weather.gov/data/obhistory/KMSN.html - [2026-10-17] Climatology: the first fall frost at the Madison Arboretum is typically around Oct 1–3 (36°F threshold, 1991–2020 normals). https://whentoplant.net/frost-dates/madison-wi/ BOTTOM LINE: The only sub-freezing event in the window so far is the Oct 17 pre-dawn freeze. NWS readings reached about 30–31°F by 03:53–06:20 CDT, but I saw no confirmed sub-30°F hourly reading. The TWC value for 04:53–07:53 CDT on Oct 17 is the main thing to check. After that, the forecast shows a sustained warm-up and CPC favors above-normal temperatures through Oct 30, so a Yes would need either a sub-30 reading this morning or a late-month cold shot. NOT FOUND: The TWC hourly observations for KMSN, including the Oct 17 04:53–07:53 CDT values and the overnight minimum. The NWS 3-day table ended at 03:53 CDT. I also found no NWS forecast discussion text and no forecast cold outbreak for Oct 25–31.

- [2026-10-17] The window opened on 2026-10-13, so the freeze of the morning of Oct 17 counts. It may already have decided the question. The NWS KMSN observation history was published at 08:53 UTC (03:53 CDT). It showed hourly readings of 36°F at 00:53, 34°F at 01:53, 32°F at 02:53 and 30.9°F at 03:53, with calm winds and clear skies. The lowest reading on that page was 30.9°F, so nothing below 30°F yet. https://forecast.weather.gov/data/obhistory/KMSN.html - [2026-10-17] The NWS API gave a KMSN observation at 11:20 UTC (06:20 CDT) of -1°C, about 30.2°F, with clear skies and calm wind. That is still not below 30°F. I could not read the readings between 04:00 and 06:20 CDT or after 06:20, so the overnight minimum is unconfirmed. Sunrise is around 07:25 CDT, and the coldest hour usually comes near sunrise. The API values are NWS data. The contract settles on The Weather Company (TWC) hourly data, which can differ by a degree or round differently. https://api.weather.gov/stations/KMSN/observations?limit=30 - [2026-10-16] NWS had a Freeze Warning for 01:00–09:00 CDT on Oct 17. The Madison point forecast gave a low around 31°F, and the Dane County zone forecast gave lows around 30. https://forecast.weather.gov/MapClick.php?lat=43.07974&lon=-89.37975 - [2026-10-16] The WISC-TV (Channel 3000) alert text said sub-freezing temperatures "as low as 28" were expected in parts of south-central Wisconsin. WMTV said on Oct 17 that temperatures would fall to the upper 20s to low 30s across much of southern Wisconsin. Forecasts for the airport itself were about 30–31°F. https://www.channel3000.com/weather/forecast/ and https://www.wmtv15news.com/2026/10/17/beautiful-fall-weather-this-weekend-into-next-week/ - [2026-10-17] Outlook for the rest of the window: WMTV expects dry, sunny weather with highs rising from the 60s to the low 70s through the week of Oct 19. CPC's 6-10 day outlook (issued Oct 15, valid Oct 21–25) shows high above-normal temperature odds east of the Rockies, with probabilities above 80% over parts of the Upper Midwest. This points to no further freeze before about Oct 26. https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html - [2026-10-16] AccuWeather's extended Madison forecast shows lows of 41°F on Oct 26, 35°F on Oct 28, and 33°F and 40°F around Oct 29–30. These are low-skill forecasts at that range, and the exact dates are not firmly legible. https://www.accuweather.com/en/us/madison/53715/october-weather/331530 - [Historical, 1991–2020 normals] A Garden.org table for Madison gives the date by which the first 28°F night has occurred. That date is Oct 15 at 30% of years and Oct 20 at 50%. By Oct 26 it is 70% of years, and by Nov 3 it is 90%. The first 32°F night has a median of about Oct 9. For the first 24°F night the median is Nov 1. A first <30°F night is therefore roughly a 50/50 event through Oct 20 and likely by Oct 31, but this table covers first occurrence of the season, not the Oct 17–31 window alone. https://garden.org/apps/frost-dates/Madison,+Wisconsin/ - [2015-09-16] UW's Weather Guys report that the airport's average first 32°F night is Oct 1, based on 73 years of records. The latest on record there was Oct 17, 1959. The Oct 16–17 freeze therefore came near the late end of the historical range. https://wxguys.ssec.wisc.edu/2015/09/16/when-does-the-first-freeze-occur-in-fall - [2026-10-16] The KMSN almanac on Weather Underground lists the normal low as 39°F for Oct 16–17. The record low for those dates is 21°F (1997). The October average low is about 43°F. https://www.wunderground.com/hourly/us/wi/madison - [2026-10-16] The Madison forecast through Oct 22 shows Oct 17 night at about 39°F and warmer nights after that. If Oct 17 did not reach below 30°F, the remaining chance depends on a cold snap in Oct 25–31. That is climatologically plausible, since typical late-October lows are about 38–41°F. https://forecast.weather.gov/MapClick.php?zoneid=WIZ063 BOTTOM LINE: The question may be settled by the Oct 17 pre-dawn minimum. NWS readings at 03:53 and 06:20 CDT were about 30.9°F and 30.2°F, just above the line, and I could not see the 04:00–06:20 CDT readings or anything after 06:20. If it did not hit below 30°F, the outlook is warm through about Oct 25. A later freeze would then need a cold snap in Oct 26–31, which climatology makes a minority-to-moderate chance. NOT FOUND: The actual TWC hourly minimum for KMSN on Oct 17. The NWS KMSN readings between 04:00 and 06:20 CDT and after 06:20 on Oct 17. An archive of past YES/NO outcomes for this contract or similar Kalshi Madison low-temperature contracts. A precise historical frequency of a <30°F hour at KMSN during Oct 17–31. CPC 8-14 day text for Madison, Oct 24–30.

YES means: TWC's official hourly KMSN temperature is strictly below 30°F (30.0°F does not count) at any observation timestamp from market open on 2026-10-13 through the end of Oct 31, 2026 (America/Chicago). - [2026-10-17] **Most likely path to YES: the Oct 17 pre-dawn freeze has already produced a sub-30 hour, or still will.** - The NWS 3-day table I fetched ends at 03:53 CDT. It shows 36, 34, 32 and 30.9°F over the previous four hours, with calm wind, clear sky and 100% relative humidity at 03:53. - Cooling had slowed to about 1°F per hour, but it had not stopped. - The 04:53, 05:53 and 06:53 hourly values are not in the sources I could read. - The obs-history page is a 3-day table that is already stale. Sunrise is after 07:00 CDT, so the usual coldest hour (near sunrise) was still ahead at 03:53. - https://forecast.weather.gov/data/obhistory/KMSN.html - [2026-10-17] **The 06:20 and 06:25 CDT API readings are rounded to whole °C, so they could hide a sub-30 value.** - The 11:20Z and 11:25Z API observations both show -1°C (flag V), with clear sky, calm wind and dewpoint -2°C, so humidity was about 93%. - A reading of -1°C is consistent with anything from about 29.5°F to 30.9°F. The previous 03:53 value of 30.9°F already rounds to that same bin. - So the API's "about 30°F" does not rule out 29.x°F. Dewpoint 1°C below air temperature meant further cooling or frost-point saturation was possible before sunrise. - https://api.weather.gov/stations/KMSN/observations/latest - [2026-10-17] **Other sources put the freeze depth below 30°F for the region.** - Fox11, published at 04:45 CDT, gave lows of mid-20s to low 30s across northeast Wisconsin and said a widespread freeze was under way. - WMTV on Oct 17 said "a hard freeze" was expected for many areas of southern Wisconsin, with upper 20s to low 30s. - A Yahoo/Journal Sentinel piece said inland south-central areas could reach 28°F, with the coldest readings away from Lake Michigan. - The airport at Truax Field sits inland from the lakes. The NWS point forecast of 31°F was 1°F above the line, which is within normal forecast error. - https://fox11online.com/news/local/chilly-freeze-frost-weekend-wisconsin-october-warning-cold - https://www.wmtv15news.com/2026/10/17/beautiful-fall-weather-this-weekend-into-next-week/ - https://www.yahoo.com/news/weather-news/articles/wisconsin-freeze-warning-temperatures-could-145246343.html - [2026-10-17] **The mechanism favors further cooling into the early morning.** - The Yahoo piece describes strong radiational cooling under clear skies and light wind, with temperatures dropping rapidly after midnight. - The obs table's calm winds and rising humidity are consistent with that. - The Oct 16 NWS forecast of widespread frost "mainly after 3am" put the frost onset right at the end of the readings I could see. - https://www.yahoo.com/news/weather-news/articles/wisconsin-freeze-warning-temperatures-could-145246343.html - [2026-10-17] **Setup was ideal for undershooting the forecast.** - Pressure was 1033 mb, one of the strongest high-pressure readings in the table. - Temperatures fell from 53°F to 31°F in 14 hours after the front passed. - The preceding days were mild, 62°F on Oct 14, so the ground held heat. Even so, the airport still reached 30.9°F by 03:53. - https://forecast.weather.gov/data/obhistory/KMSN.html - [2026-10-17] **The Oct 31 climate normal leaves room for a second chance.** - UW's Weather Guys give an average Halloween low of 34°F and a record Oct 31 low of 16°F. - They describe late-October Madison weather as highly variable from year to year. - A daily low of 34°F is only about 4°F above the threshold, and this is a typical-year figure, not a forecast. - https://wxguys.ssec.wisc.edu/page/91 - [2026-10-17] **Climatology says a sub-30 night is likely before month end.** - Garden.org's table gives the 50% date for a first 28°F night as Oct 20 and the 70% date as Oct 26. - The first 24°F night has a 20% date of Oct 23, 30% of Oct 26 and 50% of Nov 1. - A first 30°F night would fall between the 32°F and 28°F rows, around Oct 14–16 at the median. - These are first-occurrence-of-season dates, not an Oct 17–31 window probability. - https://garden.org/apps/frost-dates/Madison,+Wisconsin/ - [2026-10-16] **The NWS point forecasts, in the same sources my colleagues cited, point to a marginal outcome.** - They show a low around 31°F for the Madison point and "lows around 30" for the Dane County zone, with frost most widespread after 3–4 am. - The zone forecast's 30°F figure sits exactly on the threshold. The 7-day forecast was updated at 11:31 CDT Oct 16, before the cold air fully arrived. - The 03:53 observation was already within 1°F of the point forecast low with several hours of cooling left. - https://forecast.weather.gov/MapClick.php?lat=43.07974&lon=-89.37975 - https://forecast.weather.gov/MapClick.php?zoneid=WIZ063 - [2026-10-17] **NWS Madison's daily climate report (CLI) for Oct 17 will give the official min.** - NWS Milwaukee/Sullivan issues the Madison climate summary, and the Oct 16 report was posted at 01:40 CDT Oct 17. - The evening Oct 17 CLI will give the official Oct 17 minimum and is the best cross-check on whether an hourly value dropped below 30°F. - The report I fetched only covers Oct 16, which had a maximum of 56°F. - https://forecast.weather.gov/product.php?issuedby=MSN&product=CLI&site=mkx BOTTOM LINE: The strongest YES path is that the Oct 17 pre-dawn hours dropped below 30°F at the TWC hourly timestamps for 04:53 to 06:53 CDT. The 03:53 reading was 30.9°F and still falling, and the 06:20 whole-degree °C reading (-1°C) cannot exclude 29.x°F. The fallback path is a cold shot before Oct 31, where the average Halloween low is 34°F. NOT FOUND: The TWC hourly KMSN values for Oct 17 after 03:53 CDT. Any NWS table showing 04:53 to 06:53 CDT readings in °F. The Oct 17 CLI minimum. Any forecast showing a cold outbreak for Oct 25–31.

YES means: KMSN's minimum official TWC hourly temperature, from 2026-10-13 through the end of 2026-10-31 America/Chicago, is strictly below 30°F. - [2026-10-17] The NWS 5-minute API's last observation I could read was 11:25 UTC (6:25 CDT). It showed -1°C with a -2°C dewpoint, clear sky, calm wind and 93% humidity. ASOS converts whole °F to whole °C, so -1°C corresponds to 30–31°F (29°F would show as -2°C). That keeps KMSN at or above 30°F through 6:25 CDT. Sunrise is about 7:13 CDT, so at most about an hour of cooling remains. NO needs the 4:53–7:53 CDT hourly values to stay at 30°F or higher. https://api.weather.gov/stations/KMSN/observations?limit=15 - [2026-10-17] The NWS hourly table gives the mechanism behind the flattening cooling curve. Temperature fell 2°F per hour, then 1.1°F in the last hour. At 03:53 CDT the air was at 30.9°F with a 30.9°F dewpoint and 100% humidity. The air was saturated, so frost deposition and dewpoint-limited cooling slow further falls. The 02:53 and 01:53 observations both had a 30°F dewpoint. Winds were calm and the sky clear, but the hourly lows were stalling near 30–31°F. https://forecast.weather.gov/data/obhistory/KMSN.html - [2026-10-17] Every forecast I found for the airport itself put the Oct 17 low at 30–31°F, not below. The NWS point forecast gave about 31°F (updated Oct 16 morning). The NWS forecast for the airport itself, from Oct 15, gave 30°F. WKOW and Weather Underground gave 31°F. The "28" figures in the warning text refer to colder inland pockets. https://forecast.weather.gov/MapClick.php?lat=43.07974&lon=-89.37975 and https://www.wkow.com/weather/ - [2026-10-17] Timing helps NO. The freeze warning ran to 9 am CDT. Sunrise was at 7:13 am CDT, and Saturday's forecast high was in the 50s with a southwest wind of 10–15 mph. Mixing after sunrise ends cooling. The overnight low appears to have been near 30–31°F, with nothing below 30°F seen so far. https://forecast.weather.gov/MapClick.php?site=MKX&map.x=159&map.y=151 - [2026-10-17] The Oct 17 overnight low is not a reliable guide to what comes next. The question depends on the Oct 18–31 temperatures. Bulletins say this is a "brief chill" and that temperatures reach near 70 by midweek. The NWS Oct 16 forecast keeps lows at 39°F or higher after tonight. Nothing in the first 8 days comes near 30°F. https://www.yahoo.com/news/weather-news/articles/wisconsin-freeze-warning-temperatures-could-145246343.html - [2026-10-17] Deterministic Oct 18–25 guidance is warm. Timeanddate's Oct 18–25 lows range from 41 to 54°F. The weather-forecast.com text issued 00:00 Oct 17 has Oct 19–24 lows near 45–49°F and Oct 24 highs near 68°F. https://www.timeanddate.com/weather/usa/madison/ext and https://www.weather-forecast.com/locations/Madison/forecasts/latest - [2026-10-17] The same Oct 17 model run puts the coldest low of its whole 16 days at 33.1°F on Monday night Oct 26. It shows 33°F, not below 30°F. Its Oct 27–31 highs are 47–67°F with rain and southerly wind on Oct 30–31. Its Oct 28 and 31 wet, windy, southerly pattern is unfavorable for radiational cooling. An earlier run (Oct 13) had a "cold snap" Oct 27–28, but even that run had a low near 33°F, which shows how forecasts keep trimming late-month cold. https://www.weather-forecast.com/locations/Madison/forecasts/latest - [2026-10-13/16] The NWS Oct 16 climate report says October 16 was 4°F below normal, but the month to date is 15 heating-degree-days below normal. Temperatures are near seasonal, so there is no persistent cold pattern behind the freeze. The 80°F weekend of Oct 10–11 was well above normal. https://forecast.weather.gov/product.php?issuedby=MSN&product=CLI&site=mkx and https://www.wmtv15news.com/2026/10/11/southern-wisconsins-warm-october-days-are-numbered/ - [2026-10-17] A literal reading of the rules favors NO if the Oct 17 reading stays at 30°F or above. The question asks for a value strictly below 30°F, and exactly 30°F does not count. The wording is about "full reported precision", and the hourly TWC value may be a whole °F or °C-derived figure such as 30.2°F or 30.9°F. Observations before issuance do not count, but the Oct 17 pre-dawn hours fall inside the window since issuance was Oct 13. The Oct 17 pre-dawn reading is therefore the single most important point. A TWC reading such as 29.x°F at 4:53–7:53 CDT would resolve YES. https://www.wunderground.com/hourly/us/wi/madison - [2026-10-17] Climatology is not a strong YES argument for Oct 18–31. The last 15 days of October have normal lows of about 39–40°F falling to roughly 36°F, which needs a 6–10°F departure. The NWS Oct 17 normal low is 40°F, and record Halloween lows are 16°F (1925). A sub-30°F hour late in the month needs a strong cold front and clear, calm skies. https://wxguys.ssec.wisc.edu/category/meteorology/page/61 BOTTOM LINE: On NWS readings the Oct 17 pre-dawn low stayed at or above 30°F through 6:25 CDT, and no forecast shows anything under 33°F through Oct 31. NO is therefore the default unless an unseen TWC hourly reading from 4:53–7:53 CDT on Oct 17 was 29°F or lower, or a surprise cold shot arrives after Oct 25. NOT FOUND: The TWC hourly series for KMSN, including the 4:53–7:53 CDT values on Oct 17. NWS readings after 6:25 CDT. The NWS Madison forecast discussion text. A confirmed ECMWF/GFS ensemble cold-risk signal for Oct 26–31. A historical frequency of a sub-30°F hour at KMSN during Oct 18–31.