Was the forecast right for Boston on Mon Aug 17?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against the ECMWF IFS analysis
14 days out, 4 models put Boston's Mon Aug 17 high anywhere from 23° to 26°;by the final call, the day before, the field had settled to a median of 24°. The day verified at 24° against the ECMWF IFS analysis, with 2.5 mm of precipitation — drizzle.
ECMWF landed closest, off by 0.1°. GFS ran 3° cool.
What every model said, at every lead
Daily-high calls for Mon Aug 17 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 · 2026-08-02 | — | 28° | — | — | 24° | — | — | 24–28° |
| 14d · 2026-08-03 | 23° | 25° | 26° | — | 23° | — | — | 23–26° |
| 13d · 2026-08-04 | 24° | 26° | 23° | — | 22° | — | — | 22–26° |
| 12d · 2026-08-05 | 23° | 25° | 24° | — | 21° | — | — | 21–25° |
| 11d · 2026-08-06 | 24° | 26° | 24° | — | 23° | — | — | 23–26° |
| 10d · 2026-08-07 | 25° | 25° | 24° | — | 25° | — | — | 24–25° |
| 9d · 2026-08-08 | 28° | 23° | 21° | 26° | 27° | — | — | 21–28° |
| 8d · 2026-08-09 | 25° | 27° | 25° | 27° | 20° | — | — | 20–27° |
| 7d · 2026-08-10 | 25° | 27° | 27° | 25° | 27° | — | — | 25–27° |
| 6d · 2026-08-11 | 27° | 28° | 28° | 25° | 27° | 28° | 28° | 25–28° |
| 5d · 2026-08-12 | 28° | 29° | 29° | 24° | 27° | 29° | 26° | 24–29° |
| 4d · 2026-08-13 | 25° | 28° | 27° | 30° | 24° | 25° | 28° | 24–30° |
| 3d · 2026-08-14 | 24° | 20° | 26° | 23° | 25° | 21° | 22° | 20–26° |
| 2d · 2026-08-15 | 24° | 21° | 22° | 23° | 21° | 23° | 22° | 21–24° |
| 1d · 2026-08-16 | 24° | 22° | 24° | 25° | 21° | 23° | 25° | 21–25° |
| actual | 24° |
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.