Was the forecast right for Boston on Sat Aug 1?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against the ECMWF IFS analysis
6 days out, 7 models put Boston's Sat Aug 1 high anywhere from 22° to 30°;by the final call, the day before, the field had settled to a median of 30°. The day verified at 30° against the ECMWF IFS analysis, with 0.8 mm of precipitation — drizzle.
ICON landed closest, off by 0.2°. AIFS ran 2° cool.
What every model said, at every lead
Daily-high calls for Sat Aug 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 |
|---|---|---|---|---|---|---|---|---|
| 6d · 2026-07-26 | 24° | 30° | 28° | 26° | 22° | 26° | 30° | 22–30° |
| 5d · 2026-07-27 | 27° | 31° | 25° | 28° | 21° | 25° | 25° | 21–31° |
| 4d · 2026-07-28 | 27° | 29° | 27° | 27° | 21° | 26° | 28° | 21–29° |
| 3d · 2026-07-29 | 27° | 30° | 28° | 29° | 28° | 28° | 31° | 27–31° |
| 2d · 2026-07-30 | 27° | 28° | 27° | 28° | 28° | 28° | 28° | 27–28° |
| 1d · 2026-07-31 | 28° | 30° | 29° | 31° | 31° | 30° | 29° | 28–31° |
| actual | 30° |
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.