Which weather model is most accurate in Phoenix?
Phoenix, Arizona · daily high temperature in °F · trailing 30 days · refreshed at most every 6 hours
Every day, The Spread archives what each major weather model predicted for Phoenix at 1-, 3-, and 7-day leads, then scores those forecasts against the PHX observations once the day has happened. This page covers the trailing 30 days (2026-08-04 to 2026-09-02), for daily high temperature.
One day out, ECMWF IFS has been most accurate (typical miss 1.45°F); at three days, too close to call; at seven days, too close to call.
The largest standing bias belongs to NOAA AIGFS (AI), which has run cool by about 3.13°F at 3-day lead over this window.
The Spread's own bias-corrected blend scored a 1.37°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) in °F 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 |
|---|---|---|---|---|
| ECMWF IFS | 1.4° (-0.7°) | 2.1° (+0.1°) | 2.8° (-0.1°) | 30 |
| DWD ICON | 1.9° (-1.3°) | 2.6° (-0.8°) | — | 30 |
| NOAA GFS | 2.0° (-0.8°) | 2.1° (-0.8°) | 3.7° (-1.3°) | 30 |
| ECMWF AIFS (AI) | 2.6° (-2.2°) | 3.1° (-2.6°) | 4.1° (-2.8°) | 30 |
| UKMO (UK) | 2.9° (-2.3°) | 3.3° (-0.6°) | — | 30 |
| NOAA AIGFS (AI) | 3.0° (-2.5°) | 3.5° (-3.1°) | 3.7° (-2.9°) | 30 |
| GEM (Canada) | 3.2° (-2.1°) | 3.8° (-2.6°) | 3.0° (-1.4°) | 30 |
| NBM (US blend) | 2.2° (-1.6°) | 2.6° (-1.6°) | 3.1° (-1.6°) | 30 |
| Blended (bias-corrected) | 1.4° (+0.0°) | 1.9° (-0.0°) | 2.6° (+0.0°) | 30 |
Method, honestly
The Spread's Phoenix point is the Phoenix Sky Harbor station (PHX), 3.5 mi from downtown, used for both forecasts and verifications. 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 PHX observations — the station's own daily highs, a thermometer rather than a grid, and no correction applies: the thermometer is the truth outright. 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.
- Tue Sep 1 12 days out the models said 104–110; it hit 101. GFS led (off 0.2°F); UKMO ran 4°F cold.
- Mon Aug 31 11 days out the models said 104–112; it hit 91. ICON led (off 0.2°F); AIFS ran 3°F cold.
- Sun Aug 30 10 days out the models said 105–114; it hit 106. GFS led (off 0.0°F); AIFS ran 12°F cold.
- Sat Aug 29 9 days out the models said 106–114; it hit 113. ECMWF led (off 1.4°F); AIFS ran 9°F cold.
- Fri Aug 28 8 days out the models said 106–115; it hit 112. GFS led (off 0.1°F); AIFS ran 5°F cold.
- Thu Aug 27 7 days out the models said 107–115; it hit 113. ECMWF led (off 0.4°F); UKMO ran 4°F cold.
- Wed Aug 26 6 days out the models said 106–115; it hit 117. ECMWF led (off 0.5°F); GEM ran 6°F cold.
- Tue Aug 25 5 days out the models said 108–114; it hit 115. ECMWF led (off 1.8°F); GEM ran 5°F cold.
- Mon Aug 24 4 days out the models said 102–111; it hit 108. ICON led (off 0.4°F); UKMO ran 6°F cold.
- Sun Aug 23 3 days out the models said 102–112; it hit 113. ICON led (off 0.2°F); AIFS ran 5°F cold.
- Mon Aug 17 13 days out the models said 100–107; it hit 114. GFS led (off 0.3°F); GEM ran 4°F cold.
- Sun Aug 16 13 days out the models said 91–109; it hit 109. GFS led (off 0.5°F); UKMO ran 8°F cold.
- Sat Aug 15 13 days out the models said 88–108; it hit 108. GFS led (off 0.6°F); GEM ran 4°F cold.
- Fri Aug 14 13 days out the models said 97–106; it hit 100. ECMWF led (off 0.3°F); UKMO ran 3°F cold.
- Thu Aug 13 13 days out the models said 101–107; it hit 97. AIGFS led (off 1.0°F); ICON ran 4°F cold.
- Wed Aug 12 13 days out the models said 96–107; it hit 95. AIFS led (off 0.9°F); ECMWF ran 9°F hot.
- Tue Aug 11 13 days out the models said 96–103; it hit 103. AIGFS led (off 0.5°F); GFS ran 2°F hot.
- Mon Aug 10 13 days out the models said 88–109; it hit 108. ICON led (off 0.0°F); UKMO ran 4°F cold.
- Sun Aug 9 13 days out the models said 90–99; it hit 111. GFS led (off 0.3°F).
- Sat Aug 8 12 days out the models said 95–103; it hit 111. GEM led (off 0.2°F); ECMWF ran 3°F hot.
- Fri Aug 7 11 days out the models said 100–103; it hit 109. GEM led (off 0.1°F); ECMWF ran 3°F hot.
- Thu Aug 6 10 days out the models said 101–108; it hit 104. ECMWF led (off 0.7°F); GEM ran 6°F hot.
- Wed Aug 5 9 days out the models said 103–107; it hit 104. ECMWF led (off 0.3°F); GEM ran 3°F hot.
- Tue Aug 4 8 days out the models said 97–111; it hit 108. AIFS led (off 0.1°F); GEM ran 3°F hot.
- Mon Aug 3 7 days out the models said 110–111; it hit 114. GEM led (off 0.1°F); AIGFS ran 3°F cold.
- Sun Aug 2 6 days out the models said 110–114; it hit 114. ICON led (off 0.2°F); ECMWF ran 2°F hot.
- Sat Aug 1 5 days out the models said 106–117; it hit 114. ICON led (off 0.2°F).
- Fri Jul 31 4 days out the models said 113–116; it hit 113. AIGFS led (off 0.1°F); ECMWF ran 3°F hot.
- Thu Jul 30 3 days out the models said 111–114; it hit 113. AIFS led (off 0.1°F); AIGFS ran 2°F cold.
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