Was the forecast right for Boston on Mon Aug 17?
Boston, Massachusetts · daily high temperature in °F · 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 73° to 78°;by the final call, the day before, the field had settled to a median of 74°. The day verified at 76° against the ECMWF IFS analysis, with 0.1 in of precipitation — drizzle.
ECMWF landed closest, off by 0.2°. GFS ran 6° 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 | — | 83° | — | — | 74° | — | — | 74–83° |
| 14d · 2026-08-03 | 74° | 77° | 78° | — | 73° | — | — | 73–78° |
| 13d · 2026-08-04 | 76° | 79° | 74° | — | 71° | — | — | 71–79° |
| 12d · 2026-08-05 | 74° | 78° | 76° | — | 70° | — | — | 70–78° |
| 11d · 2026-08-06 | 75° | 79° | 74° | — | 73° | — | — | 73–79° |
| 10d · 2026-08-07 | 77° | 77° | 75° | — | 77° | — | — | 75–77° |
| 9d · 2026-08-08 | 82° | 74° | 70° | 79° | 80° | — | — | 70–82° |
| 8d · 2026-08-09 | 76° | 81° | 77° | 81° | 69° | — | — | 69–81° |
| 7d · 2026-08-10 | 77° | 80° | 81° | 78° | 80° | — | — | 77–81° |
| 6d · 2026-08-11 | 81° | 83° | 82° | 77° | 80° | 83° | 83° | 77–83° |
| 5d · 2026-08-12 | 83° | 84° | 85° | 76° | 80° | 84° | 78° | 76–85° |
| 4d · 2026-08-13 | 77° | 83° | 80° | 85° | 74° | 77° | 82° | 74–85° |
| 3d · 2026-08-14 | 74° | 68° | 80° | 73° | 77° | 70° | 72° | 68–80° |
| 2d · 2026-08-15 | 75° | 70° | 72° | 73° | 71° | 73° | 72° | 70–75° |
| 1d · 2026-08-16 | 74° | 71° | 76° | 77° | 70° | 74° | 77° | 70–77° |
| actual | 76° |
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.