Was the forecast right for Boston on Sun Aug 30?
Boston, Massachusetts · daily high temperature in °F · forecasts from each model's archived runs, verified against the BOS observations
11 days out, 4 models put Boston's Sun Aug 30 high anywhere from 74° to 78°;by the final call, the day before, the field had settled to a median of 85°. The day verified at 86° against the BOS observations — drizzle.
ICON landed closest, off by 0.0°. AIFS ran 4° cool.
What every model said, at every lead
Daily-high calls for Sun Aug 30 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 |
|---|---|---|---|---|---|---|---|---|
| 11d · 2026-08-19 | 76° | 74° | 76° | — | 78° | — | — | 74–78° |
| 10d · 2026-08-20 | 74° | 74° | 77° | — | 75° | — | — | 74–77° |
| 9d · 2026-08-21 | 71° | 83° | 70° | 68° | 80° | — | — | 68–83° |
| 8d · 2026-08-22 | 80° | 73° | 80° | 73° | 76° | — | — | 73–80° |
| 7d · 2026-08-23 | 74° | 79° | 83° | 72° | 70° | — | — | 70–83° |
| 6d · 2026-08-24 | 81° | 80° | 84° | 74° | 81° | 83° | 72° | 72–84° |
| 5d · 2026-08-25 | 80° | 81° | 84° | 78° | 86° | 84° | 81° | 78–86° |
| 4d · 2026-08-26 | 83° | 83° | 87° | 76° | 86° | 85° | 87° | 76–87° |
| 3d · 2026-08-27 | 82° | 84° | 84° | 82° | 85° | 85° | 84° | 82–85° |
| 2d · 2026-08-28 | 81° | 83° | 85° | 84° | 84° | 84° | 86° | 81–86° |
| 1d · 2026-08-29 | 82° | 82° | 86° | 89° | 84° | 86° | 85° | 82–89° |
| actual | 86° |
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 receipt was settled, usually 2 days after the date; a correction published after that is not carried into it. Archive depth varies by city; receipts exist only for dates the archive watched arrive.