WEATHER · FORECAST CHANGE

Highest temperature in Philadelphia on Oct 21, 2026: PBE moves “69° or above” up to 46% from 31%

New forecast guidance reached the model between 14:02 UTC and 17:00 UTC on Oct 20. Same model version, later data cutoff: here is exactly which inputs changed.

Published October 20, 2026 at 17:17 UTCModel data as of Oct 20 17:00ZBy the PropBetEdge Predictions Desk1 min read

Photo: 颐园居 · CC BY-SA 4.0 · Wikimedia Commons

31%46%

69° or above · pbe-weather-maxtemp@1.1.0 · 14:02 UTC → 17:00 UTC

Move+15 pts

Market at capture8%

Inputs changed2primary

LIVE UPDATE · not part of the original story

Highest temperature in Philadelphia on Oct 21, 2026?

69° or above · PRE-WINDOW

PBE46%0 pts since publication

Kalshi6%0 pts since publication

Gap+40

RESEARCH PBE Oct 20 17:00Z · market

Open the live forecast →

Quick read

pbe-weather-maxtemp@1.1.0 moved “69° or above” from 31% to 46% (+15 pts).
Later data cutoff: Oct 20 11:00Z → Oct 20 17:00Z; same model version, so the move reflects inputs, not a model change.
Primary inputs changed: National Blend spread, National Blend of Models forecast high.
The Kalshi mid captured with each snapshot went from 6% to 8%.

What changed in the inputs

Between the snapshot captured at Oct 20 14:02Z (data cutoff Oct 20 11:00Z) and the one at Oct 20 17:00Z (cutoff Oct 20 17:00Z), the same model version — pbe-weather-maxtemp@1.1.0 — moved “69° or above” from 31% to 46%. The model inputs that changed: National Blend spread from 2°F to 1°F; National Blend of Models forecast high from 67°F to 68°F.

EVIDENCEStored model inputs, before and afterFrom the immutable feature snapshots attached to each forecast

Input	Before	After	Primary
Guidance lead time	23h	17h	—
National Blend spread	2°F	1°F	yes
National Blend of Models forecast high	67°F	68°F	yes

Units: as labeledAs of Oct 20 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“69° or above”: pbe-weather-maxtemp@1.1.0 snapshots vs the marketSame model version only; the dashed line is the stored Kalshi mid

Kalshi mid (stored observations)PBE pbe-weather-maxtemp@1.1.0 snapshots

Units: % probabilityAs of Oct 20 17:00ZSource: PBE forecast archive; Kalshi

Data table

Time (UTC)	Source	Value %
Oct 20 14:02Z	PBE pbe-weather-maxtemp@1.1.0	31
Oct 20 14:02Z	Kalshi mid	6
Oct 20 14:06Z	Kalshi mid	9
Oct 20 14:12Z	Kalshi mid	9
Oct 20 14:16Z	Kalshi mid	7
Oct 20 14:18Z	Kalshi mid	7
Oct 20 14:20Z	Kalshi mid	7
Oct 20 15:00Z	Kalshi mid	7
Oct 20 15:02Z	Kalshi mid	6
Oct 20 15:04Z	Kalshi mid	6
Oct 20 15:16Z	Kalshi mid	6
Oct 20 15:22Z	Kalshi mid	7
Oct 20 15:24Z	Kalshi mid	8
Oct 20 16:00Z	Kalshi mid	8
Oct 20 16:18Z	Kalshi mid	8
Oct 20 17:00Z	PBE pbe-weather-maxtemp@1.1.0	46
Oct 20 17:00Z	Kalshi mid	8

The Kalshi mid captured with each snapshot went from 6% to 8%.

The two snapshots

	Earlier	Later
Captured	Oct 20 14:02Z	Oct 20 17:00Z
Data cutoff	Oct 20 11:00Z	Oct 20 17:00Z
Guidance runs	NWS GFS MOS 2026-10-20T06Z, NWS National Blend of Models 2026-10-20T06Z	NWS GFS MOS 2026-10-20T12Z, NWS National Blend of Models 2026-10-20T12Z
PBE	31%	46%
Market at capture	6%	8%

Evidence & method

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

69° or above

Model: pbe-weather-maxtemp@1.1.0 · RESEARCH
Snapshot: 4bcd0ea3-032c-472e-9512-9eb8a0f6a3c8
Compared with: 153ced9a-cb6f-4bd5-bc81-f49e761276b5
Captured: Oct 20 17:00Z
Data cutoff: Oct 20 17:00Z
Market observation: 8% · 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 CLIPHL (weather.com/kalshi)
Independent check: NWS Daily Climate Report CLIPHL (WFO PHI); NOAA RCC-ACIS USW00013739
Measurement: Maximum temperature for the climate day 2026-10-21, 00:00-24:00 local standard time (UTC-5)
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 Philadelphia (CLIPHL) for Oct 21, 2026, is greater than 68° 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.