Was the forecast right for Boston on Fri Sep 18?
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 Fri Sep 18 high anywhere from 17° to 25°; by the final call the field had settled to a median of 26°. The day verified at 27° against the BOS observations — drizzle.
GEM landed closest, off by 0.4°. AIFS ran 2° cold.
What every model said, at every lead
Daily-high calls for Fri Sep 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 Boston scoreboard shows them, labelled.
| Lead | AIFS | AIGFS | ECMWF | GEM | GFS | ICON | UKMO | Range |
|---|---|---|---|---|---|---|---|---|
| 15d · 2026-09-03 | — | 25° | — | — | 19° | — | — | 19–25° |
| 14d · 2026-09-04 | 17° | 25° | — | — | 21° | — | — | 17–25° |
| 13d · 2026-09-05 | 25° | 19° | 25° | — | 17° | — | — | 17–25° |
| 12d · 2026-09-06 | 27° | 28° | 19° | — | 18° | — | — | 18–28° |
| 11d · 2026-09-07 | 23° | 19° | 24° | — | 17° | — | — | 17–24° |
| 10d · 2026-09-08 | 26° | 31° | 19° | — | 24° | — | — | 19–31° |
| 9d · 2026-09-09 | 28° | 31° | 22° | — | 23° | — | — | 22–31° |
| 8d · 2026-09-10 | 27° | 26° | 21° | 18° | 19° | — | — | 18–27° |
| 7d · 2026-09-11 | 22° | 21° | 21° | 19° | 21° | — | — | 19–22° |
| 6d · 2026-09-12 | 22° | 19° | 22° | 23° | 23° | 23° | — | 19–23° |
| 5d · 2026-09-13 | 23° | 21° | 26° | 23° | 19° | 20° | 21° | 19–26° |
| 4d · 2026-09-14 | 23° | 23° | 25° | 24° | 23° | 24° | 24° | 23–25° |
| 3d · 2026-09-15 | 24° | 26° | 24° | 24° | 24° | 24° | 26° | 24–26° |
| 2d · 2026-09-16 | 24° | 26° | 25° | 25° | 25° | 25° | 26° | 24–26° |
| 1d · 2026-09-17 | 24° | 25° | 25° | 27° | 24° | 26° | 25° | 24–27° |
| 0d · 2026-09-18 | 25° | 26° | 26° | 27° | 25° | 25° | 26° | 25–27° |
| actual | 27° |
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.