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Chicago — photograph (Photo: J. Crocker · Attribution · via Wikimedia Commons)
WEATHER · FORECAST CHANGE

Highest temperature in Chicago on Oct 19, 2026: PBE moves “64° or below” down to 7% from 21%

New forecast guidance reached the model between 14:00 UTC and 17:00 UTC on Oct 18. Same model version, later data cutoff: here is exactly which inputs changed.

Published Model data as of Oct 18 17:00ZBy the PropBetEdge Predictions Desk1 min read

Photo: J. Crocker · Attribution · Wikimedia Commons

21%7%

64° or below · pbe-weather-maxtemp@1.1.0 · 14:00 UTC → 17:00 UTC

Move−14 pts
Market at capture3%
Inputs changed2primary
LIVE UPDATE · not part of the original story

Highest temperature in Chicago on Oct 19, 2026?

64° or below · PRE-WINDOW

PBE7%0 pts since publication
Kalshi4%+1 pts since publication
Gap+3

RESEARCH PBE Oct 18 17:00Z · market

Open the live forecast →

Quick read

  • pbe-weather-maxtemp@1.1.0 moved “64° or below” from 21% to 7% (−14 pts).
  • Later data cutoff: Oct 18 11:00Z → Oct 18 17:00Z; same model version, so the move reflects inputs, not a model change.
  • Primary inputs changed: GFS MOS forecast high, National Blend of Models forecast high.
  • A comparable market observation was not captured with both snapshots, so no market move is stated.

What changed in the inputs

Between the snapshot captured at Oct 18 14:00Z (data cutoff Oct 18 11:00Z) and the one at Oct 18 17:00Z (cutoff Oct 18 17:00Z), the same model version — pbe-weather-maxtemp@1.1.0 — moved “64° or below” from 21% to 7%. The model inputs that changed: GFS MOS forecast high from 68°F to 69°F; National Blend of Models forecast high from 66°F to 68°F.

EVIDENCEStored model inputs, before and afterFrom the immutable feature snapshots attached to each forecast
InputBeforeAfterPrimary
Guidance lead time24h18h—
GFS MOS forecast high68°F69°Fyes
National Blend of Models forecast high66°F68°Fyes
Units: as labeledAs of Oct 18 17:00ZSource: PBE feature snapshots

This page reports which stored inputs differ between two immutable forecasts. It does not claim why the underlying weather guidance changed.

The forecast path

PROBABILITY HISTORY“64° or below”: pbe-weather-maxtemp@1.1.0 snapshots vs the marketSame model version only; the dashed line is the stored Kalshi mid
0%25%50%75%100%Oct 18 14:00ZOct 18 15:30ZOct 18 17:00Z21%7%PBE pbe-weather-maxtemp@1.1.0 snapshots 21% · Oct 18 14:00ZPBE pbe-weather-maxtemp@1.1.0 snapshots 7% · Oct 18 17:00Z
Kalshi mid (stored observations)PBE pbe-weather-maxtemp@1.1.0 snapshots
Units: % probabilityAs of Oct 18 17:00ZSource: PBE forecast archive; Kalshi
Data table
Time (UTC)SourceValue %
Oct 18 14:00ZPBE pbe-weather-maxtemp@1.1.021
Oct 18 14:06ZKalshi mid9
Oct 18 14:08ZKalshi mid8
Oct 18 14:12ZKalshi mid9
Oct 18 14:16ZKalshi mid9
Oct 18 14:26ZKalshi mid7
Oct 18 14:54ZKalshi mid4
Oct 18 14:56ZKalshi mid4
Oct 18 15:00ZKalshi mid4
Oct 18 15:12ZKalshi mid6
Oct 18 15:14ZKalshi mid6
Oct 18 15:40ZKalshi mid6
Oct 18 15:50ZKalshi mid5
Oct 18 15:56ZKalshi mid5
Oct 18 16:00ZKalshi mid4
Oct 18 16:04ZKalshi mid4
Oct 18 16:06ZKalshi mid3
Oct 18 17:00ZPBE pbe-weather-maxtemp@1.1.07
Oct 18 17:00ZKalshi mid3

A comparable market observation was not captured with both snapshots, so no market move is stated.

The two snapshots

EarlierLater
CapturedOct 18 14:00ZOct 18 17:00Z
Data cutoffOct 18 11:00ZOct 18 17:00Z
Guidance runsNWS GFS MOS 2026-10-18T06Z, NWS National Blend of Models 2026-10-18T06ZNWS GFS MOS 2026-10-18T12Z, NWS National Blend of Models 2026-10-18T12Z
PBE21%7%
Market at capture—3%

Evidence & method

What this story is based on. Every value above was read from these immutable records.

64° or below
Model
pbe-weather-maxtemp@1.1.0 · RESEARCH
Snapshot
ced49dc3-9224-4f85-829d-318462540ee8
Compared with
e0b60343-5434-4981-a746-1c494007cb44
Captured
Oct 18 17:00Z
Data cutoff
Oct 18 17:00Z
Market observation
3% · captured with the snapshot
Source families
NOAA/NWS via Iowa Environmental Mesonet archive · NOAA Regional Climate Centers ACIS · NOAA/NWS api.weather.gov
RESOLUTION RULE
Resolves on
The Weather Company (weather.com/kalshi) — The Weather Company daily maximum temperature for CLIMDW (weather.com/kalshi)
Independent check
NWS Daily Climate Report CLIMDW (WFO LOT); NOAA RCC-ACIS USW00014819
Measurement
Maximum temperature for the climate day 2026-10-19, 00:00-24:00 local standard time (UTC-6)
Rounding
Whole degrees Fahrenheit as reported; preliminary values may differ by rounding/conversion
Exceptions
Preliminary data may be revised; the exchange may hold expiration until a non-erroneous revision, else last fair price
If the maximum temperature recorded at Chicago (CLIMDW) for Oct 19, 2026, is less than 65° fahrenheit according to The Weather Company, then the market resolves to Yes.
MODEL LIMITATIONS
  • Pre-window only; no current-conditions input
  • Guidance can run cold/hot in unusual regimes (see LA diagnostic, 2026-10-04)

Weather · daily high — inputs: National Blend of Models day max (GFS MOS fallback) + station empirical guidance-error tables. This model on the research board →

Market prices are a benchmark only and never enter a PropBetEdge model. Research-stage probabilities; not advice.