Was the forecast right for Chicago on Mon Sep 21?
Chicago, Illinois · daily high temperature in °C · forecasts from each model's archived runs, verified against the MDW observations
14 days out, 4 models put Chicago's Mon Sep 21 high anywhere from 20° to 28°;by the final call, the day before, the field had settled to a median of 17°. The day verified at 18° against the MDW observations, with 0.5 mm of precipitation — drizzle.
ECMWF landed closest, off by 0.1°. AIGFS ran 2° cool.
What every model said, at every lead
Daily-high calls for Mon Sep 21 as each model's runs approached it — the last archived run per day. NBM and The Spread's own blend are consensus products and stay out of these ranges and rankings; the Chicago scoreboard shows them, labelled.
| Lead | AIFS | AIGFS | ECMWF | GEM | GFS | ICON | UKMO | Range |
|---|---|---|---|---|---|---|---|---|
| 15d · 2026-09-06 | — | 16° | — | — | 22° | — | — | 16–22° |
| 14d · 2026-09-07 | 20° | 26° | 23° | — | 28° | — | — | 20–28° |
| 13d · 2026-09-08 | 21° | 18° | 18° | — | 20° | — | — | 18–21° |
| 12d · 2026-09-09 | 28° | 21° | 16° | — | 23° | — | — | 16–28° |
| 11d · 2026-09-10 | 18° | 15° | 16° | — | 19° | — | — | 15–19° |
| 10d · 2026-09-11 | 19° | 19° | 26° | — | 27° | — | — | 19–27° |
| 9d · 2026-09-12 | 21° | 17° | 18° | 19° | 24° | — | — | 17–24° |
| 8d · 2026-09-13 | 24° | 19° | 25° | 26° | 16° | — | — | 16–26° |
| 7d · 2026-09-14 | 18° | 20° | 20° | 20° | 16° | — | — | 16–20° |
| 6d · 2026-09-15 | 18° | 17° | 24° | 18° | 23° | 20° | 19° | 17–24° |
| 5d · 2026-09-16 | 18° | 16° | 19° | 19° | 18° | 23° | 19° | 16–23° |
| 4d · 2026-09-17 | 18° | 17° | 17° | 16° | 16° | 18° | 20° | 16–20° |
| 3d · 2026-09-18 | 18° | 17° | 18° | 16° | 17° | 19° | 19° | 16–19° |
| 2d · 2026-09-19 | 18° | 17° | 18° | 18° | 18° | 19° | 19° | 17–19° |
| 1d · 2026-09-20 | 17° | 16° | 18° | 17° | 17° | 18° | 20° | 16–20° |
| actual | 18° |
Read it honestly
This is one date, not a league table. A model can win a day it deserved to lose; rankings only mean something over a window. For that, see which model has been most accurate in Chicago — or every city The Spread scores.
Forecasts are what each model's archived runs said at the time, captured at The Spread's sweep times — never reconstructed after the fact. Truth is the MDW observations. Archive depth varies by city; receipts exist only for dates the archive watched arrive.