Was the forecast right for Boston on Wed Sep 30?
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 Wed Sep 30 high anywhere from 15° to 23°;by the final call, the day before, the field had settled to a median of 21°. The day verified at 19° against the BOS observations, with 0.3 mm of precipitation — drizzle.
AIFS landed closest, off by 0.3°. GEM ran 3° warm.
What every model said, at every lead
Daily-high calls for Wed Sep 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 |
|---|---|---|---|---|---|---|---|---|
| 15d · 2026-09-15 | — | 16° | — | — | 27° | — | — | 16–27° |
| 14d · 2026-09-16 | 20° | 15° | 15° | — | 23° | — | — | 15–23° |
| 13d · 2026-09-17 | 17° | 25° | 23° | — | 16° | — | — | 16–25° |
| 12d · 2026-09-18 | 23° | 21° | 24° | — | 17° | — | — | 17–24° |
| 11d · 2026-09-19 | 17° | 15° | 17° | — | 17° | — | — | 15–17° |
| 10d · 2026-09-20 | 21° | 23° | 18° | — | 22° | — | — | 18–23° |
| 9d · 2026-09-21 | 22° | 24° | 15° | 22° | 20° | — | — | 15–24° |
| 8d · 2026-09-22 | 22° | 25° | 18° | 21° | 23° | — | — | 18–25° |
| 7d · 2026-09-23 | 22° | 25° | 22° | 23° | 19° | — | — | 19–25° |
| 6d · 2026-09-24 | 22° | 22° | 22° | 20° | 20° | 22° | 20° | 20–22° |
| 5d · 2026-09-25 | 21° | 23° | 21° | 19° | 21° | 22° | 20° | 19–23° |
| 4d · 2026-09-26 | 20° | 21° | 20° | 19° | 20° | 21° | 20° | 19–21° |
| 3d · 2026-09-27 | 19° | 21° | 22° | 21° | 20° | 21° | 21° | 19–22° |
| 2d · 2026-09-28 | 19° | 21° | 20° | 21° | 20° | 21° | 21° | 19–21° |
| 1d · 2026-09-29 | 19° | 21° | 21° | 22° | 20° | 22° | 21° | 19–22° |
| actual | 19° |
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.