Was the forecast right for Boston on Sun Aug 9?
Boston, Massachusetts · daily high temperature in °F · forecasts from each model's archived runs, verified against ERA5
13 days out, 4 models put Boston's Sun Aug 9 high anywhere from 76° to 85°; by the final call the field had settled to a median of 91°. ERA5 says the day verified at 91° — drizzle.
GFS landed closest, off by 0.1°. AIFS ran 3° cold.
What every model said, at every lead
Daily-high calls for Sun Aug 9 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 · 2026-07-27 | 85° | 76° | 83° | — | 84° | — | — | 76–85° |
| 12d · 2026-07-28 | 85° | 85° | 90° | — | 84° | — | — | 84–90° |
| 11d · 2026-07-29 | 85° | 92° | 93° | — | 80° | — | — | 80–93° |
| 10d · 2026-07-30 | 76° | 87° | 86° | — | 73° | — | — | 73–87° |
| 9d · 2026-07-31 | 81° | 92° | 83° | — | 88° | — | — | 81–92° |
| 8d · 2026-08-01 | 82° | 96° | 83° | 90° | 87° | — | — | 82–96° |
| 7d · 2026-08-02 | 85° | 87° | 81° | 89° | 90° | — | — | 81–90° |
| 6d · 2026-08-03 | 88° | 94° | 86° | 87° | 91° | 93° | — | 86–94° |
| 5d · 2026-08-04 | 86° | 93° | 88° | 86° | 88° | 92° | 88° | 86–93° |
| 4d · 2026-08-05 | 88° | 93° | 90° | 87° | 88° | 90° | 88° | 87–93° |
| 3d · 2026-08-06 | 87° | 94° | 92° | 88° | 91° | 89° | 88° | 87–94° |
| 2d · 2026-08-07 | 88° | 93° | 91° | 89° | 90° | 92° | 93° | 88–93° |
| 1d · 2026-08-08 | 88° | 93° | 92° | 91° | 91° | 91° | 91° | 88–93° |
| 0d · 2026-08-09 | 88° | 92° | 91° | 92° | 91° | 91° | 92° | 88–92° |
| actual | 91° |
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 ERA5 reanalysis (temperature_2m_max). Archive depth varies by city; receipts exist only for dates the archive watched arrive.