Was the forecast right for Chicago on Tue Aug 18?
Chicago, Illinois · daily high temperature in °F · forecasts from each model's archived runs, verified against the ECMWF IFS analysis
13 days out, 4 models put Chicago's Tue Aug 18 high anywhere from 76° to 80°; by the final call the field had settled to a median of 80°. The day verified at 83° against the ECMWF IFS analysis, with 0.34 in of precipitation — thunderstorms.
ICON landed closest, off by 0.8°. AIFS ran 5° cold.
What every model said, at every lead
Daily-high calls for Tue Aug 18 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 · 2026-08-03 | — | 76° | — | — | 74° | — | — | 74–76° |
| 14d · 2026-08-04 | 78° | 75° | — | — | 75° | — | — | 75–78° |
| 13d · 2026-08-05 | 80° | 78° | 79° | — | 76° | — | — | 76–80° |
| 12d · 2026-08-06 | 76° | 76° | 80° | — | 72° | — | — | 72–80° |
| 11d · 2026-08-07 | 78° | 76° | 70° | — | 87° | — | — | 70–87° |
| 10d · 2026-08-08 | 79° | 80° | 78° | — | 82° | — | — | 78–82° |
| 9d · 2026-08-09 | 79° | 74° | 71° | — | 80° | — | — | 71–80° |
| 8d · 2026-08-10 | 78° | 80° | 78° | 79° | 78° | — | — | 78–80° |
| 7d · 2026-08-11 | 78° | 79° | 80° | 80° | 81° | — | — | 78–81° |
| 6d · 2026-08-12 | 78° | 81° | 80° | 79° | 82° | 83° | — | 78–83° |
| 5d · 2026-08-13 | 77° | 82° | 79° | 79° | 81° | 87° | 83° | 77–87° |
| 4d · 2026-08-14 | 78° | 80° | 81° | 77° | 83° | 82° | 87° | 77–87° |
| 3d · 2026-08-15 | 79° | 82° | 81° | 79° | 83° | 83° | 82° | 79–83° |
| 2d · 2026-08-16 | 79° | 83° | 82° | 81° | 83° | 82° | 86° | 79–86° |
| 1d · 2026-08-17 | 78° | 81° | 80° | 85° | 78° | 82° | 84° | 78–85° |
| 0d · 2026-08-18 | 78° | 81° | 80° | 85° | 78° | 82° | 80° | 78–85° |
| actual | 83° |
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 ECMWF IFS analysis (temperature_2m_max). Archive depth varies by city; receipts exist only for dates the archive watched arrive.