Was the forecast right for Boston on Sun Sep 6?
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 Sun Sep 6 high anywhere from 66° to 74°; by the final call the field had settled to a median of 68°. The day verified at 68° against the BOS observations, with 0.11 in of precipitation — drizzle.
AIFS landed closest, off by 0.2°. GEM ran 3° hot.
What every model said, at every lead
Daily-high calls for Sun Sep 6 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 · 2026-08-22 | — | 80° | — | — | 66° | — | — | 66–80° |
| 14d · 2026-08-23 | 66° | 69° | — | — | 71° | — | — | 66–71° |
| 13d · 2026-08-24 | 68° | 73° | 74° | — | 66° | — | — | 66–74° |
| 12d · 2026-08-25 | 85° | 70° | 78° | — | 79° | — | — | 70–85° |
| 11d · 2026-08-26 | 74° | 80° | 78° | — | 68° | — | — | 68–80° |
| 10d · 2026-08-27 | 74° | 90° | 73° | — | 67° | — | — | 67–90° |
| 9d · 2026-08-28 | 77° | 76° | 66° | — | 71° | — | — | 66–77° |
| 8d · 2026-08-29 | 71° | 70° | 71° | 71° | 70° | — | — | 70–71° |
| 7d · 2026-08-30 | 71° | 72° | 67° | 65° | 70° | — | — | 65–72° |
| 6d · 2026-08-31 | 71° | 65° | 64° | 68° | 65° | 65° | — | 64–71° |
| 5d · 2026-09-01 | 71° | 62° | 68° | 70° | 67° | 72° | 75° | 62–75° |
| 4d · 2026-09-02 | 74° | 69° | 66° | 73° | 72° | 70° | 67° | 66–74° |
| 3d · 2026-09-03 | 69° | 70° | 66° | 71° | 68° | 72° | 68° | 66–72° |
| 2d · 2026-09-04 | 70° | 69° | 67° | 74° | 69° | 71° | 70° | 67–74° |
| 1d · 2026-09-05 | 69° | 68° | 68° | 72° | 69° | 70° | 69° | 68–72° |
| 0d · 2026-09-06 | 68° | 66° | 67° | 71° | 68° | 69° | 70° | 66–71° |
| actual | 68° |
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.