Was the forecast right for Boston on Mon Sep 21?
Boston, Massachusetts · daily high temperature in °F · forecasts from each model's archived runs, verified against the BOS observations
14 days out, 4 models put Boston's Mon Sep 21 high anywhere from 64° to 73°;by the final call, the day before, the field had settled to a median of 64°. The day verified at 65° against the BOS observations, with 0.01 in of precipitation — drizzle.
UKMO landed closest, off by 0.2°. ICON ran 2° warm.
What every model said, at every lead
Daily-high calls for Mon Sep 21 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 · 2026-09-06 | — | 60° | — | — | 69° | — | — | 60–69° |
| 14d · 2026-09-07 | 64° | 72° | 69° | — | 73° | — | — | 64–73° |
| 13d · 2026-09-08 | 67° | 61° | 85° | — | 60° | — | — | 60–85° |
| 12d · 2026-09-09 | 72° | 58° | 63° | — | 66° | — | — | 58–72° |
| 11d · 2026-09-10 | 61° | 61° | 65° | — | 57° | — | — | 57–65° |
| 10d · 2026-09-11 | 61° | 65° | 67° | — | 64° | — | — | 61–67° |
| 9d · 2026-09-12 | 65° | 63° | 66° | 62° | 59° | — | — | 59–66° |
| 8d · 2026-09-13 | 63° | 66° | 69° | 69° | 60° | — | — | 60–69° |
| 7d · 2026-09-14 | 63° | 64° | 68° | 62° | 62° | — | — | 62–68° |
| 6d · 2026-09-15 | 65° | 63° | 67° | 63° | 61° | 68° | 67° | 61–68° |
| 5d · 2026-09-16 | 66° | 64° | 64° | 61° | 63° | 64° | 63° | 61–66° |
| 4d · 2026-09-17 | 66° | 64° | 62° | 60° | 62° | 68° | 67° | 60–68° |
| 3d · 2026-09-18 | 65° | 63° | 64° | 63° | 62° | 66° | 65° | 62–66° |
| 2d · 2026-09-19 | 64° | 64° | 63° | 64° | 63° | 67° | 66° | 63–67° |
| 1d · 2026-09-20 | 64° | 64° | 64° | 67° | 64° | 67° | 65° | 64–67° |
| actual | 65° |
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.