Was the forecast right for Boston on Sun Sep 20?
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 20 high anywhere from 60° to 73°; by the final call the field had settled to a median of 61°. The day verified at 63° against the BOS observations, with 0.1 in of precipitation — drizzle.
ECMWF landed closest, off by 0.4°. AIGFS ran 4° cool.
What every model said, at every lead
Daily-high calls for Sun Sep 20 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 · 2026-09-05 | — | 72° | — | — | 78° | — | — | 72–78° |
| 14d · 2026-09-06 | 70° | 68° | — | — | 61° | — | — | 61–70° |
| 13d · 2026-09-07 | 73° | 60° | 69° | — | 70° | — | — | 60–73° |
| 12d · 2026-09-08 | 67° | 71° | 76° | — | 69° | — | — | 67–76° |
| 11d · 2026-09-09 | 66° | 63° | 66° | — | 75° | — | — | 63–75° |
| 10d · 2026-09-10 | 69° | 76° | 66° | — | 75° | — | — | 66–76° |
| 9d · 2026-09-11 | 65° | 73° | 64° | — | 61° | — | — | 61–73° |
| 8d · 2026-09-12 | 73° | 71° | 80° | 68° | 69° | — | — | 68–80° |
| 7d · 2026-09-13 | 75° | 74° | 65° | 76° | 62° | — | — | 62–76° |
| 6d · 2026-09-14 | 65° | 62° | 73° | 74° | 68° | 72° | — | 62–74° |
| 5d · 2026-09-15 | 61° | 57° | 69° | 62° | 62° | 66° | 70° | 57–70° |
| 4d · 2026-09-16 | 62° | 59° | 63° | 63° | 60° | 62° | 66° | 59–66° |
| 3d · 2026-09-17 | 62° | 58° | 62° | 65° | 59° | 61° | 69° | 58–69° |
| 2d · 2026-09-18 | 61° | 60° | 63° | 66° | 65° | 60° | 67° | 60–67° |
| 1d · 2026-09-19 | 62° | 57° | 64° | 64° | 61° | 62° | 65° | 57–65° |
| 0d · 2026-09-20 | 61° | 59° | 63° | 62° | 61° | 59° | 64° | 59–64° |
| actual | 63° |
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.