Was the forecast right for Boston on Fri Sep 4?
Boston, Massachusetts · daily high temperature in °F · forecasts from each model's archived runs, verified against the BOS observations
13 days out, 4 models put Boston's Fri Sep 4 high anywhere from 69° to 81°; by the final call the field had settled to a median of 82°. The day verified at 85° against the BOS observations — drizzle.
GEM landed closest, off by 0.4°. AIFS ran 5° cold.
What every model said, at every lead
Daily-high calls for Fri Sep 4 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 · 2026-08-20 | — | 73° | — | — | 74° | — | — | 73–74° |
| 14d · 2026-08-21 | 68° | 85° | — | — | 65° | — | — | 65–85° |
| 13d · 2026-08-22 | 81° | 72° | 72° | — | 69° | — | — | 69–81° |
| 12d · 2026-08-23 | 76° | 67° | 77° | — | 85° | — | — | 67–85° |
| 11d · 2026-08-24 | 72° | 60° | 68° | — | 64° | — | — | 60–72° |
| 10d · 2026-08-25 | 81° | 64° | 86° | — | 64° | — | — | 64–86° |
| 9d · 2026-08-26 | 74° | 74° | 85° | — | 67° | — | — | 67–85° |
| 8d · 2026-08-27 | 77° | 74° | 70° | 73° | 66° | — | — | 66–77° |
| 7d · 2026-08-28 | 78° | 77° | 78° | 74° | 79° | — | — | 74–79° |
| 6d · 2026-08-29 | 78° | 77° | 73° | 74° | 67° | 84° | — | 67–84° |
| 5d · 2026-08-30 | 79° | 81° | 72° | 71° | 80° | 80° | 70° | 70–81° |
| 4d · 2026-08-31 | 80° | 79° | 79° | 77° | 74° | 81° | 84° | 74–84° |
| 3d · 2026-09-01 | 80° | 80° | 81° | 76° | 78° | 82° | 83° | 76–83° |
| 2d · 2026-09-02 | 80° | 81° | 81° | 81° | 82° | 83° | 84° | 80–84° |
| 1d · 2026-09-03 | 80° | 82° | 82° | 81° | 79° | 84° | 83° | 79–84° |
| 0d · 2026-09-04 | 80° | 82° | 80° | 85° | 81° | 82° | 83° | 80–85° |
| actual | 85° |
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.