Was the forecast right for Boston on Sun Sep 13?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against the BOS observations
13 days out, 4 models put Boston's Sun Sep 13 high anywhere from 23° to 25°; by the final call the field had settled to a median of 20°. The day verified at 21° against the BOS observations, with 21.3 mm of precipitation — thunderstorms.
ICON landed closest, off by 0.0°. AIGFS ran 2° cold.
What every model said, at every lead
Daily-high calls for Sun Sep 13 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 Boston scoreboard shows them, labelled.
| Lead | AIFS | AIGFS | ECMWF | GEM | GFS | ICON | UKMO | Range |
|---|---|---|---|---|---|---|---|---|
| 15d · 2026-08-29 | — | 23° | — | — | 22° | — | — | 22–23° |
| 14d · 2026-08-30 | 25° | 23° | — | — | 18° | — | — | 18–25° |
| 13d · 2026-08-31 | 25° | 23° | 23° | — | 23° | — | — | 23–25° |
| 12d · 2026-09-01 | 30° | 28° | 30° | — | 25° | — | — | 25–30° |
| 11d · 2026-09-02 | 21° | 33° | 19° | — | 27° | — | — | 19–33° |
| 10d · 2026-09-03 | 21° | 28° | 21° | — | 26° | — | — | 21–28° |
| 9d · 2026-09-04 | 26° | 24° | 25° | — | 22° | — | — | 22–26° |
| 8d · 2026-09-05 | 25° | 24° | 25° | 27° | 27° | — | — | 24–27° |
| 7d · 2026-09-06 | 28° | 30° | 29° | 24° | 27° | — | — | 24–30° |
| 6d · 2026-09-07 | 26° | 28° | 27° | 25° | 28° | 29° | — | 25–29° |
| 5d · 2026-09-08 | 24° | 26° | 26° | 23° | 26° | 26° | 28° | 23–28° |
| 4d · 2026-09-09 | 22° | 19° | 24° | 20° | 23° | 25° | 28° | 19–28° |
| 3d · 2026-09-10 | 21° | 21° | 23° | 21° | 25° | 24° | 23° | 21–25° |
| 2d · 2026-09-11 | 22° | 19° | 25° | 25° | 20° | 23° | 24° | 19–25° |
| 1d · 2026-09-12 | 21° | 19° | 22° | 22° | 19° | 22° | 20° | 19–22° |
| 0d · 2026-09-13 | 20° | 19° | 21° | 21° | 20° | 21° | 20° | 19–21° |
| actual | 21° |
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 Boston — 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 BOS observations. Archive depth varies by city; receipts exist only for dates the archive watched arrive.