Was the forecast right for Chicago on Mon Aug 31?
Chicago, Illinois · daily high temperature in °F · forecasts from each model's archived runs, verified against the MDW observations
10 days out, 4 models put Chicago's Mon Aug 31 high anywhere from 80° to 96°; by the final call the field had settled to a median of 89°. The day verified at 91° against the MDW observations, with 0.2 in of precipitation — thunderstorms.
GFS landed closest, off by 0.6°. AIFS ran 6° cold.
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 |
|---|---|---|---|---|---|---|---|---|
| 10d · 2026-08-21 | 83° | 85° | 80° | — | 96° | — | — | 80–96° |
| 9d · 2026-08-22 | 80° | 87° | 76° | — | 82° | — | — | 76–87° |
| 8d · 2026-08-23 | 87° | 78° | 80° | 87° | 81° | — | — | 78–87° |
| 7d · 2026-08-24 | 88° | 93° | 88° | 86° | 86° | — | — | 86–93° |
| 6d · 2026-08-25 | 84° | 83° | 87° | 88° | 88° | 84° | — | 83–88° |
| 5d · 2026-08-26 | 89° | 92° | 95° | 93° | 93° | 91° | 93° | 89–95° |
| 4d · 2026-08-27 | 89° | 90° | 92° | 89° | 94° | 92° | 91° | 89–94° |
| 3d · 2026-08-28 | 87° | 90° | 90° | 92° | 93° | 90° | 92° | 87–93° |
| 2d · 2026-08-29 | 87° | 86° | 88° | 92° | 91° | 88° | 94° | 86–94° |
| 1d · 2026-08-30 | 89° | 86° | 86° | 93° | 88° | 93° | 93° | 86–93° |
| 0d · 2026-08-31 | 86° | 89° | 88° | 94° | 92° | 90° | 89° | 86–94° |
| actual | 91° |
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.