Was the forecast right for Boston on Sun Aug 23?
Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against the BOS observations
4 days out, 7 models put Boston's Sun Aug 23 high anywhere from 21° to 29°;by the final call, the day before, the field had settled to a median of 24°. The day verified at 22° against the BOS observations, with 9.7 mm of precipitation — showers.
GEM landed closest, off by 0.7°. UKMO ran 3° warm.
What every model said, at every lead
Daily-high calls for Sun Aug 23 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 |
|---|---|---|---|---|---|---|---|---|
| 4d · 2026-08-19 | 24° | 23° | 26° | 21° | 21° | 29° | 24° | 21–29° |
| 3d · 2026-08-20 | 23° | 24° | 27° | 23° | 20° | 24° | 23° | 20–27° |
| 2d · 2026-08-21 | 23° | 25° | 27° | 24° | 22° | 23° | 21° | 21–27° |
| 1d · 2026-08-22 | 24° | 24° | 23° | 22° | 24° | 23° | 25° | 22–25° |
| actual | 22° |
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 BOS observations. 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.