Which weather model is most accurate in Seattle?
Seattle, Washington · daily high temperature · trailing 30 days · refreshed at most every 6 hours
Every day, The Spread archives what each major weather model predicted for Seattle at 1-, 3-, and 7-day leads, then scores those forecasts against ERA5 reanalysis once the day has happened. This page covers the trailing 30 days (2026-07-06 to 2026-08-05), for daily high temperature.
One day out, UKMO (UK) has been most accurate (typical miss 1.37°F); at three days, ECMWF IFS (2°F); at seven days, GEM (Canada) (3.53°F).
The largest standing bias belongs to NOAA GFS, which has run warm by about 4.64°F at 3-day lead over this window.
The Spread's own bias-corrected blend scored a 1.12°F typical miss at one day. Its corrections come from the same window it is scored on (in-sample), so read it as a ceiling, not a promise.
The scoreboard
Typical miss (MAE) with the signed bias in parentheses — positive bias means the model ran warm. Days = scored days behind the 1-day number.
| Model | 1-day | 3-day | 7-day | Days |
|---|---|---|---|---|
| UKMO (UK) | 1.4° (+0.7°) | 2.3° (+0.5°) | — | 30 |
| ECMWF IFS | 1.4° (+0.8°) | 2.0° (+0.1°) | 5.4° (+2.0°) | 30 |
| GEM (Canada) | 1.6° (+1.2°) | 3.0° (-1.7°) | 3.5° (-0.8°) | 30 |
| NOAA GFS | 2.1° (-0.7°) | 5.4° (+4.6°) | 5.6° (+3.9°) | 30 |
| NOAA AIGFS (AI) | 2.4° (+1.6°) | 2.7° (+1.1°) | 4.4° (+0.3°) | 30 |
| DWD ICON | 2.4° (-2.3°) | 3.2° (-1.7°) | — | 30 |
| ECMWF AIFS (AI) | 2.7° (-2.5°) | 3.0° (-2.7°) | 4.3° (-3.3°) | 30 |
| NBM (US blend) | 1.8° (+0.3°) | 2.2° (+0.3°) | 3.4° (+0.7°) | 30 |
| Blended (bias-corrected) | 1.1° (-0.0°) | 2.0° (-0.0°) | 3.2° (-0.0°) | 30 |
Method, honestly
Forecasts come from each model's actual archived runs via Open-Meteo's Previous Runs API — what the model said at the time, not a reconstruction. Truth is ERA5 reanalysis daily highs. Rankings cover the models themselves; the two consensus products at the bottom of the table — NBM, which is itself a blend of models, and The Spread's own bias-corrected blend — are shown for comparison, never ranked or named "most accurate" here. The blend's corrections come from the same trailing window it is scored on (in-sample), so treat its score as a ceiling. A rolling 30-day window means these numbers move — that is the point.
Receipts — was the forecast right?
One page per settled date: what every model said as the day approached, what happened, and who was closest.
- Mon Aug 3 14 days out the models said 74–96; it hit 74. ECMWF led (off 0.6°); AIGFS ran 4° hot.
- Sun Aug 2 14 days out the models said 67–84; it hit 69. ECMWF led (off 0.2°); AIGFS ran 5° cold.
- Sat Aug 1 14 days out the models said 71–83; it hit 73. GEM led (off 0.7°); AIFS ran 4° cold.
- Fri Jul 31 14 days out the models said 73–92; it hit 82. ECMWF led (off 0.2°); AIGFS ran 6° hot.
- Thu Jul 30 13 days out the models said 70–87; it hit 76. UKMO led (off 0.4°); AIGFS ran 3° hot.
- Wed Jul 29 12 days out the models said 71–85; it hit 73. GFS led (off 0.5°); AIGFS ran 6° hot.
- Tue Jul 28 11 days out the models said 69–86; it hit 74. UKMO led (off 0.1°); GFS ran 3° cold.
- Mon Jul 27 10 days out the models said 66–80; it hit 78. GEM led (off 0.0°); AIFS ran 3° cold.
- Sun Jul 26 9 days out the models said 68–80; it hit 72. GEM led (off 0.0°); ICON ran 5° cold.
- Sat Jul 25 8 days out the models said 72–78; it hit 71. ECMWF led (off 1.3°); ICON ran 4° cold.
- Fri Jul 24 7 days out the models said 75–87; it hit 79. ICON led (off 0.6°); AIFS ran 3° cold.
- Thu Jul 23 6 days out the models said 73–90; it hit 75. ECMWF led (off 0.2°); AIFS ran 6° cold.
- Wed Jul 22 5 days out the models said 79–90; it hit 88. UKMO led (off 0.1°); AIGFS ran 5° hot.
- Tue Jul 21 4 days out the models said 80–90; it hit 89. GEM led (off 0.7°); ICON ran 6° cold.
- Mon Jul 20 3 days out the models said 75–88; it hit 79. GFS led (off 0.2°); AIGFS ran 4° hot.
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