Was the forecast right for Chicago on Mon Aug 31?
Chicago, Illinois · daily high temperature in °C · forecasts from each model's archived runs, verified against the MDW observations
11 days out, 4 models put Chicago's Mon Aug 31 high anywhere from 22° to 31°;by the final call, the day before, the field had settled to a median of 32°. The day verified at 33° against the MDW observations, with 5.1 mm of precipitation — thunderstorms.
GEM landed closest, off by 0.1°. AIFS ran 2° cool.
What every model said, at every lead
Daily-high calls for Mon Aug 31 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 |
|---|---|---|---|---|---|---|---|---|
| 11d · 2026-08-20 | 22° | 31° | 27° | — | 27° | — | — | 22–31° |
| 10d · 2026-08-21 | 29° | 27° | 26° | — | 33° | — | — | 26–33° |
| 9d · 2026-08-22 | 28° | 30° | 25° | 31° | 26° | — | — | 25–31° |
| 8d · 2026-08-23 | 31° | 22° | 30° | 30° | 29° | — | — | 22–31° |
| 7d · 2026-08-24 | 29° | 30° | 31° | 32° | 32° | — | — | 29–32° |
| 6d · 2026-08-25 | 31° | 32° | 31° | 32° | 24° | 28° | 33° | 24–33° |
| 5d · 2026-08-26 | 32° | 33° | 30° | 34° | 31° | 31° | 28° | 28–34° |
| 4d · 2026-08-27 | 31° | 32° | 31° | 32° | 34° | 34° | 34° | 31–34° |
| 3d · 2026-08-28 | 31° | 31° | 32° | 31° | 33° | 33° | 33° | 31–33° |
| 2d · 2026-08-29 | 31° | 30° | 30° | 31° | 32° | 31° | 34° | 30–34° |
| 1d · 2026-08-30 | 30° | 31° | 31° | 33° | 32° | 32° | 34° | 30–34° |
| actual | 33° |
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. The actual values are the ones in hand when this receipt was settled, usually 2 days after the date; a correction published after that is not carried into it. Archive depth varies by city; receipts exist only for dates the archive watched arrive.