Was the forecast right for Philadelphia on Sun Sep 20?
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 Sun Sep 20 high anywhere from 20° to 25°; by the final call the field had settled to a median of 25°. The day verified at 26° against the PHL observations, with 5.6 mm of precipitation — showers.
GEM landed closest, off by 0.2°. ECMWF ran 1° warm.
What every model said, at every lead
Daily-high calls for Sun Sep 20 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 · 2026-09-05 | — | 24° | — | — | 32° | — | — | 24–32° |
| 14d · 2026-09-06 | 24° | 20° | — | — | 22° | — | — | 20–24° |
| 13d · 2026-09-07 | 25° | 20° | 24° | — | 22° | — | — | 20–25° |
| 12d · 2026-09-08 | 21° | 22° | 23° | — | 22° | — | — | 21–23° |
| 11d · 2026-09-09 | 22° | 31° | 26° | — | 27° | — | — | 22–31° |
| 10d · 2026-09-10 | 25° | 24° | 23° | — | 25° | — | — | 23–25° |
| 9d · 2026-09-11 | 23° | 25° | 25° | — | 21° | — | — | 21–25° |
| 8d · 2026-09-12 | 26° | 22° | 28° | 22° | 26° | — | — | 22–28° |
| 7d · 2026-09-13 | 23° | 25° | 27° | 26° | 29° | — | — | 23–29° |
| 6d · 2026-09-14 | 24° | 26° | 31° | 29° | 32° | 26° | — | 24–32° |
| 5d · 2026-09-15 | 24° | 23° | 22° | 28° | 27° | 26° | 26° | 22–28° |
| 4d · 2026-09-16 | 23° | 27° | 23° | 27° | 27° | 23° | 25° | 23–27° |
| 3d · 2026-09-17 | 23° | 23° | 27° | 26° | 24° | 25° | 24° | 23–27° |
| 2d · 2026-09-18 | 24° | 23° | 27° | 25° | 25° | 25° | 25° | 23–27° |
| 1d · 2026-09-19 | 25° | 24° | 27° | 26° | 25° | 26° | 28° | 24–28° |
| 0d · 2026-09-20 | 25° | 25° | 27° | 25° | 24° | 25° | 26° | 24–27° |
| actual | 26° |
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.