Was the forecast right for Philadelphia on Sun Sep 20?
Philadelphia, Pennsylvania · daily high temperature in °F · 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 68° to 77°; by the final call the field had settled to a median of 77°. The day verified at 78° against the PHL observations, with 0.22 in of precipitation — showers.
GEM landed closest, off by 0.4°. ECMWF ran 2° 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 | — | 75° | — | — | 89° | — | — | 75–89° |
| 14d · 2026-09-06 | 74° | 67° | — | — | 72° | — | — | 67–74° |
| 13d · 2026-09-07 | 77° | 68° | 76° | — | 72° | — | — | 68–77° |
| 12d · 2026-09-08 | 70° | 72° | 73° | — | 71° | — | — | 70–73° |
| 11d · 2026-09-09 | 72° | 87° | 78° | — | 81° | — | — | 72–87° |
| 10d · 2026-09-10 | 76° | 76° | 73° | — | 77° | — | — | 73–77° |
| 9d · 2026-09-11 | 73° | 77° | 77° | — | 70° | — | — | 70–77° |
| 8d · 2026-09-12 | 79° | 72° | 82° | 72° | 78° | — | — | 72–82° |
| 7d · 2026-09-13 | 73° | 77° | 80° | 80° | 84° | — | — | 73–84° |
| 6d · 2026-09-14 | 75° | 78° | 89° | 84° | 90° | 78° | — | 75–90° |
| 5d · 2026-09-15 | 75° | 73° | 72° | 83° | 80° | 79° | 78° | 72–83° |
| 4d · 2026-09-16 | 73° | 81° | 73° | 81° | 80° | 73° | 77° | 73–81° |
| 3d · 2026-09-17 | 74° | 73° | 81° | 79° | 75° | 77° | 74° | 73–81° |
| 2d · 2026-09-18 | 75° | 73° | 81° | 77° | 78° | 77° | 78° | 73–81° |
| 1d · 2026-09-19 | 77° | 75° | 81° | 78° | 77° | 78° | 82° | 75–82° |
| 0d · 2026-09-20 | 77° | 77° | 80° | 78° | 76° | 77° | 79° | 76–80° |
| actual | 78° |
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.