Was the forecast right for Boston on Fri Sep 18?
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 18 high anywhere from 62° to 76°; by the final call the field had settled to a median of 78°. The day verified at 80° against the BOS observations — drizzle.
GEM landed closest, off by 0.7°. AIFS ran 3° 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 | — | 77° | — | — | 67° | — | — | 67–77° |
| 14d · 2026-09-04 | 63° | 76° | — | — | 70° | — | — | 63–76° |
| 13d · 2026-09-05 | 76° | 66° | 76° | — | 62° | — | — | 62–76° |
| 12d · 2026-09-06 | 81° | 82° | 66° | — | 65° | — | — | 65–82° |
| 11d · 2026-09-07 | 73° | 66° | 75° | — | 63° | — | — | 63–75° |
| 10d · 2026-09-08 | 80° | 89° | 65° | — | 75° | — | — | 65–89° |
| 9d · 2026-09-09 | 83° | 87° | 71° | — | 73° | — | — | 71–87° |
| 8d · 2026-09-10 | 80° | 80° | 70° | 64° | 66° | — | — | 64–80° |
| 7d · 2026-09-11 | 72° | 70° | 70° | 67° | 70° | — | — | 67–72° |
| 6d · 2026-09-12 | 71° | 66° | 72° | 73° | 73° | 73° | — | 66–73° |
| 5d · 2026-09-13 | 74° | 70° | 78° | 73° | 66° | 68° | 70° | 66–78° |
| 4d · 2026-09-14 | 74° | 74° | 77° | 74° | 74° | 75° | 74° | 74–77° |
| 3d · 2026-09-15 | 76° | 78° | 76° | 75° | 75° | 76° | 78° | 75–78° |
| 2d · 2026-09-16 | 76° | 79° | 76° | 77° | 78° | 77° | 78° | 76–79° |
| 1d · 2026-09-17 | 76° | 77° | 77° | 80° | 76° | 79° | 77° | 76–80° |
| 0d · 2026-09-18 | 77° | 78° | 78° | 81° | 78° | 78° | 78° | 77–81° |
| actual | 80° |
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.