Was the forecast right for Philadelphia on Thu Sep 17?
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 Thu Sep 17 high anywhere from 22° to 30°; by the final call the field had settled to a median of 30°. The day verified at 29° against the PHL observations, with 0.8 mm of precipitation — showers.
ICON landed closest, off by 0.1°. GFS ran 3° hot.
What every model said, at every lead
Daily-high calls for Thu Sep 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 Philadelphia scoreboard shows them, labelled.
| Lead | AIFS | AIGFS | ECMWF | GEM | GFS | ICON | UKMO | Range |
|---|---|---|---|---|---|---|---|---|
| 15d · 2026-09-02 | — | 22° | — | — | 36° | — | — | 22–36° |
| 14d · 2026-09-03 | 27° | 27° | — | — | 21° | — | — | 21–27° |
| 13d · 2026-09-04 | 27° | 22° | 24° | — | 30° | — | — | 22–30° |
| 12d · 2026-09-05 | 35° | 27° | 27° | — | 18° | — | — | 18–35° |
| 11d · 2026-09-06 | 28° | 31° | 22° | — | 20° | — | — | 20–31° |
| 10d · 2026-09-07 | 27° | 22° | 24° | — | 23° | — | — | 22–27° |
| 9d · 2026-09-08 | 30° | 27° | 25° | — | 26° | — | — | 25–30° |
| 8d · 2026-09-09 | 30° | 28° | 22° | 33° | 28° | — | — | 22–33° |
| 7d · 2026-09-10 | 29° | 29° | 28° | 30° | 30° | — | — | 28–30° |
| 6d · 2026-09-11 | 31° | 30° | 29° | 29° | 30° | 32° | — | 29–32° |
| 5d · 2026-09-12 | 30° | 27° | 28° | 30° | 30° | 30° | 29° | 27–30° |
| 4d · 2026-09-13 | 29° | 28° | 29° | 29° | 30° | 29° | 28° | 28–30° |
| 3d · 2026-09-14 | 29° | 28° | 28° | 30° | 29° | 29° | 28° | 28–30° |
| 2d · 2026-09-15 | 29° | 29° | 30° | 29° | 31° | 30° | 27° | 27–31° |
| 1d · 2026-09-16 | 29° | 29° | 31° | 29° | 31° | 28° | 28° | 28–31° |
| 0d · 2026-09-17 | 29° | 30° | 30° | 29° | 32° | 29° | 30° | 29–32° |
| actual | 29° |
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.