Was the forecast right for Boston on Thu Sep 10?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against the BOS observations
14 days out, 4 models put Boston's Thu Sep 10 high anywhere from 21° to 30°;by the final call, the day before, the field had settled to a median of 29°. The day verified at 31° against the BOS observations, with 0.3 mm of precipitation — drizzle.
GEM landed closest, off by 0.2°. ECMWF ran 2° cool.
What every model said, at every lead
Daily-high calls for Thu Sep 10 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, labeled.
| Lead | AIFS | AIGFS | ECMWF | GEM | GFS | ICON | UKMO | Range |
|---|---|---|---|---|---|---|---|---|
| 15d · 2026-08-26 | — | 27° | — | — | 26° | — | — | 26–27° |
| 14d · 2026-08-27 | 30° | 24° | 30° | — | 21° | — | — | 21–30° |
| 13d · 2026-08-28 | 27° | 30° | 34° | — | 29° | — | — | 27–34° |
| 12d · 2026-08-29 | 25° | 30° | 27° | — | 28° | — | — | 25–30° |
| 11d · 2026-08-30 | 28° | 26° | 20° | — | 20° | — | — | 20–28° |
| 10d · 2026-08-31 | 30° | 31° | 25° | — | 31° | — | — | 25–31° |
| 9d · 2026-09-01 | 28° | 21° | 30° | 29° | 24° | — | — | 21–30° |
| 8d · 2026-09-02 | 28° | 31° | 28° | 28° | 27° | — | — | 27–31° |
| 7d · 2026-09-03 | 25° | 30° | 26° | 28° | 30° | — | — | 25–30° |
| 6d · 2026-09-04 | 28° | 30° | 30° | 28° | 23° | 31° | 31° | 23–31° |
| 5d · 2026-09-05 | 28° | 30° | 29° | 27° | 22° | 30° | 27° | 22–30° |
| 4d · 2026-09-06 | 29° | 30° | 27° | 26° | 30° | 30° | 29° | 26–30° |
| 3d · 2026-09-07 | 29° | 30° | 27° | 30° | 30° | 29° | 30° | 27–30° |
| 2d · 2026-09-08 | 29° | 31° | 29° | 30° | 30° | 30° | 29° | 29–31° |
| 1d · 2026-09-09 | 29° | 31° | 29° | 31° | 29° | 29° | 29° | 29–31° |
| actual | 31° |
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. The actual values are the ones in hand when this day was verified, usually 2 days after the date; a correction published after that is not carried into it. Archive depth varies by city; verified days exist only for dates the archive watched arrive.