Was the forecast right for Boston on Tue Sep 1?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against the BOS observations
13 days out, 4 models put Boston's Tue Sep 1 high anywhere from 21° to 30°;by the final call, the day before, the field had settled to a median of 20°. The day verified at 21° against the BOS observations, with 6.6 mm of precipitation — showers.
ICON landed closest, off by 0.1°. UKMO ran 2° warm.
What every model said, at every lead
Daily-high calls for Tue Sep 1 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 |
|---|---|---|---|---|---|---|---|---|
| 13d · 2026-08-19 | 24° | 30° | 24° | — | 21° | — | — | 21–30° |
| 12d · 2026-08-20 | 22° | 34° | 29° | — | 32° | — | — | 22–34° |
| 11d · 2026-08-21 | 26° | 31° | 22° | — | 29° | — | — | 22–31° |
| 10d · 2026-08-22 | 22° | 23° | 23° | — | 22° | — | — | 22–23° |
| 9d · 2026-08-23 | 25° | 23° | 22° | 29° | 21° | — | — | 21–29° |
| 8d · 2026-08-24 | 24° | 33° | 24° | 26° | 24° | — | — | 24–33° |
| 7d · 2026-08-25 | 27° | 31° | 32° | 23° | 19° | — | — | 19–32° |
| 6d · 2026-08-26 | 23° | 21° | 26° | 23° | 21° | 23° | 32° | 21–32° |
| 5d · 2026-08-27 | 23° | 20° | 24° | 22° | 19° | 24° | 25° | 19–25° |
| 4d · 2026-08-28 | 23° | 23° | 22° | 21° | 22° | 25° | 26° | 21–26° |
| 3d · 2026-08-29 | 21° | 20° | 27° | 21° | 21° | 21° | 21° | 20–27° |
| 2d · 2026-08-30 | 20° | 19° | 22° | 21° | 20° | 20° | 22° | 19–22° |
| 1d · 2026-08-31 | 20° | 19° | 22° | 22° | 20° | 20° | 23° | 19–23° |
| actual | 21° |
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.