Was the forecast right for Boston on Mon Aug 10?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against ERA5
13 days out, 4 models put Boston's Mon Aug 10 high anywhere from 25° to 34°; by the final call the field had settled to a median of 31°. ERA5 says the day verified at 29° — cloudy.
ICON landed closest, off by 0.2°. ECMWF ran 2° hot.
What every model said, at every lead
Daily-high calls for Mon Aug 10 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 |
|---|---|---|---|---|---|---|---|---|
| 14d · 2026-07-27 | 28° | 25° | — | — | 26° | — | — | 25–28° |
| 13d · 2026-07-28 | 25° | 29° | 28° | — | 34° | — | — | 25–34° |
| 12d · 2026-07-29 | 28° | 30° | 33° | — | 24° | — | — | 24–33° |
| 11d · 2026-07-30 | 28° | 32° | 32° | — | 23° | — | — | 23–32° |
| 10d · 2026-07-31 | 30° | 26° | 32° | — | 32° | — | — | 26–32° |
| 9d · 2026-08-01 | 30° | 33° | 28° | — | 29° | — | — | 28–33° |
| 8d · 2026-08-02 | 30° | 32° | 30° | 29° | 33° | — | — | 29–33° |
| 7d · 2026-08-03 | 31° | 34° | 32° | 32° | 32° | — | — | 31–34° |
| 6d · 2026-08-04 | 30° | 34° | 30° | 31° | 31° | 34° | — | 30–34° |
| 5d · 2026-08-05 | 30° | 34° | 32° | 32° | 32° | 34° | 33° | 30–34° |
| 4d · 2026-08-06 | 30° | 32° | 32° | 31° | 31° | 34° | 33° | 30–34° |
| 3d · 2026-08-07 | 29° | 32° | 32° | 30° | 28° | 30° | 32° | 28–32° |
| 2d · 2026-08-08 | 30° | 32° | 32° | 31° | 28° | 32° | 33° | 28–33° |
| 1d · 2026-08-09 | 30° | 32° | 33° | 34° | 33° | 33° | 34° | 30–34° |
| 0d · 2026-08-10 | 29° | 31° | 32° | 31° | 31° | 29° | 30° | 29–32° |
| actual | 29° |
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.