Was the forecast right for Philadelphia on Fri Sep 18?
Philadelphia, Pennsylvania · daily high temperature in °C · forecasts from each model's archived runs, verified against the PHL observations
13 days out, 4 models put Philadelphia's Fri Sep 18 high anywhere from 21° to 29°; by the final call the field had settled to a median of 29°. The day verified at 31° against the PHL observations — drizzle.
AIFS landed closest, off by 0.3°. GFS ran 4° cold.
What every model said, at every lead
Daily-high calls for Fri Sep 18 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 Philadelphia scoreboard shows them, labelled.
| Lead | AIFS | AIGFS | ECMWF | GEM | GFS | ICON | UKMO | Range |
|---|---|---|---|---|---|---|---|---|
| 15d · 2026-09-03 | — | 27° | — | — | 21° | — | — | 21–27° |
| 14d · 2026-09-04 | — | 24° | — | — | 28° | — | — | 24–28° |
| 13d · 2026-09-05 | 29° | 21° | 29° | — | 21° | — | — | 21–29° |
| 12d · 2026-09-06 | 29° | 29° | 27° | — | 24° | — | — | 24–29° |
| 11d · 2026-09-07 | 26° | 22° | 27° | — | 21° | — | — | 21–27° |
| 10d · 2026-09-08 | 33° | 29° | 20° | — | 27° | — | — | 20–33° |
| 9d · 2026-09-09 | 32° | 28° | 27° | — | 27° | — | — | 27–32° |
| 8d · 2026-09-10 | 31° | 27° | 23° | 22° | 23° | — | — | 22–31° |
| 7d · 2026-09-11 | 28° | 25° | 26° | 26° | 32° | — | — | 25–32° |
| 6d · 2026-09-12 | 26° | 29° | 30° | 31° | 26° | 26° | — | 26–31° |
| 5d · 2026-09-13 | 28° | 21° | 29° | 30° | 27° | 25° | 27° | 21–30° |
| 4d · 2026-09-14 | 29° | 29° | 30° | 29° | 30° | 28° | 29° | 28–30° |
| 3d · 2026-09-15 | 30° | 28° | 28° | 28° | 30° | 27° | 29° | 27–30° |
| 2d · 2026-09-16 | 29° | 29° | 29° | 28° | 30° | 28° | 29° | 28–30° |
| 1d · 2026-09-17 | 30° | 29° | 30° | 28° | 29° | 28° | 28° | 28–30° |
| 0d · 2026-09-18 | 30° | 28° | 29° | 28° | 26° | 29° | 29° | 26–30° |
| actual | 31° |
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 Philadelphia — 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 PHL observations. Archive depth varies by city; receipts exist only for dates the archive watched arrive.