Was the forecast right for Boston on Sat Aug 8?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against the ECMWF IFS analysis
13 days out, 4 models put Boston's Sat Aug 8 high anywhere from 24° to 34°;by the final call, the day before, the field had settled to a median of 33°. The day verified at 34° against the ECMWF IFS analysis, with 4.6 mm of precipitation — rain.
GFS landed closest, off by 0.9°. AIFS ran 4° cool.
What every model said, at every lead
Daily-high calls for Sat Aug 8 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 · 2026-07-26 | 24° | 25° | 34° | — | 28° | — | — | 24–34° |
| 12d · 2026-07-27 | 31° | 30° | 30° | — | 27° | — | — | 27–31° |
| 11d · 2026-07-28 | 31° | 31° | 30° | — | 21° | — | — | 21–31° |
| 10d · 2026-07-29 | 29° | 32° | 28° | — | 31° | — | — | 28–32° |
| 9d · 2026-07-30 | 28° | 35° | 30° | 34° | 30° | — | — | 28–35° |
| 8d · 2026-07-31 | 30° | 34° | 29° | 30° | 31° | — | — | 29–34° |
| 7d · 2026-08-01 | 28° | 35° | 30° | 32° | 27° | — | — | 27–35° |
| 6d · 2026-08-02 | 28° | 34° | 33° | 32° | 30° | 26° | 32° | 26–34° |
| 5d · 2026-08-03 | 29° | 32° | 32° | 26° | 28° | 30° | 30° | 26–32° |
| 4d · 2026-08-04 | 30° | 33° | 31° | 30° | 31° | 32° | 34° | 30–34° |
| 3d · 2026-08-05 | 30° | 33° | 32° | 33° | 30° | 33° | 34° | 30–34° |
| 2d · 2026-08-06 | 30° | 33° | 33° | 27° | 30° | 33° | 34° | 27–34° |
| 1d · 2026-08-07 | 30° | 32° | 33° | 33° | 33° | 33° | 32° | 30–33° |
| actual | 34° |
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 ECMWF IFS analysis (temperature_2m_max). 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.