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
11 days out, 4 models put Chicago's Mon Aug 31 high anywhere from 72° to 88°;by the final call, the day before, 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.
GEM landed closest, off by 0.1°. AIFS ran 4° 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 | 72° | 88° | 80° | — | 81° | — | — | 72–88° |
| 10d · 2026-08-21 | 84° | 81° | 79° | — | 92° | — | — | 79–92° |
| 9d · 2026-08-22 | 83° | 86° | 77° | 87° | 80° | — | — | 77–87° |
| 8d · 2026-08-23 | 87° | 72° | 87° | 87° | 84° | — | — | 72–87° |
| 7d · 2026-08-24 | 84° | 87° | 88° | 90° | 90° | — | — | 84–90° |
| 6d · 2026-08-25 | 88° | 90° | 88° | 90° | 74° | 83° | 92° | 74–92° |
| 5d · 2026-08-26 | 89° | 92° | 86° | 94° | 87° | 89° | 82° | 82–94° |
| 4d · 2026-08-27 | 88° | 90° | 87° | 89° | 93° | 93° | 92° | 87–93° |
| 3d · 2026-08-28 | 88° | 88° | 90° | 88° | 91° | 91° | 92° | 88–92° |
| 2d · 2026-08-29 | 87° | 85° | 86° | 87° | 90° | 88° | 93° | 85–93° |
| 1d · 2026-08-30 | 87° | 87° | 88° | 91° | 89° | 90° | 93° | 87–93° |
| 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. 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.