Was the forecast right for Boston on Fri Jul 31?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against the ECMWF IFS analysis
5 days out, 7 models put Boston's Fri Jul 31 high anywhere from 20° to 26°;by the final call, the day before, the field had settled to a median of 25°. The day verified at 25° against the ECMWF IFS analysis, with 2.5 mm of precipitation — drizzle.
AIFS landed closest, off by 0.1°. GFS ran 3° warm.
What every model said, at every lead
Daily-high calls for Fri Jul 31 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 |
|---|---|---|---|---|---|---|---|---|
| 5d · 2026-07-26 | 22° | 25° | 26° | 20° | 20° | 24° | 25° | 20–26° |
| 4d · 2026-07-27 | 24° | 26° | 22° | 21° | 19° | 21° | 23° | 19–26° |
| 3d · 2026-07-28 | 24° | 24° | 22° | 25° | 20° | 22° | 24° | 20–25° |
| 2d · 2026-07-29 | 24° | 24° | 25° | 24° | 23° | 25° | 27° | 23–27° |
| 1d · 2026-07-30 | 25° | 25° | 24° | 25° | 27° | 24° | 24° | 24–27° |
| actual | 25° |
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.