The Spread

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

10 days out, 4 models put Chicago's Mon Aug 31 high anywhere from 27° to 35°; by the final call 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.

GFS landed closest, off by 0.3°. AIFS ran 3° cold.

10 days out the models said 27–35; it hit 33. GFS led (off 0.3°C); AIFS ran 3°C cold.
The shareable card for this receipt — what this page looks like pasted into a thread.

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 AIFSAIGFSECMWFGEMGFSICONUKMO Range
10d · 2026-08-21 28° 30° 27° — 35° — — 27–35°
9d · 2026-08-22 27° 31° 24° — 28° — — 24–31°
8d · 2026-08-23 30° 26° 27° 31° 27° — — 26–31°
7d · 2026-08-24 31° 34° 31° 30° 30° — — 30–34°
6d · 2026-08-25 29° 28° 30° 31° 31° 29° — 28–31°
5d · 2026-08-26 32° 33° 35° 34° 34° 33° 34° 32–35°
4d · 2026-08-27 32° 32° 33° 31° 34° 33° 33° 31–34°
3d · 2026-08-28 31° 32° 32° 33° 34° 32° 34° 31–34°
2d · 2026-08-29 31° 30° 31° 33° 33° 31° 34° 30–34°
1d · 2026-08-30 32° 30° 30° 34° 31° 34° 34° 30–34°
0d · 2026-08-31 30° 32° 31° 34° 33° 32° 32° 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. Archive depth varies by city; receipts exist only for dates the archive watched arrive.