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Which weather model is most accurate in Phoenix?

Forecast Highs Lows Rain Model accuracy

Phoenix, Arizona · daily high temperature in °F · trailing 30 days, through Fri Oct 16

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 (2026-09-17 to 2026-10-16), for daily high temperature.

One day out, too close to call; 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 1-day lead over this window.

Phoenix's full forecast, every model day by day, with the record on this page beside it. Request an invite; it's free during the beta.

The scoreboard

Typical miss (MAE) in °F with the bias in parentheses. Bias is the mean signed error of the predicted daily high — positive means the model ran warm. A model's high is the warmest of its hourly values and the station's is the warmest it got at any moment, so a model's high reads a little cool, and its low a little warm, even on a day it gets every hour right. ECMWF IFS gives a value only every 3 hours (every 6 past day 6), and ECMWF AIFS (AI) and NOAA AIGFS (AI) only every 6, with the hours between filled in, so their highs read cooler still and their lows warmer. In the forecasts scored here GFS also steps to every 3 hours from day 5, ICON and GEM from day 4, and UKMO from day 3, every 6 by day 6. Days = scored days behind the 1-day number.

Model 1-day 3-day 7-day Days
ECMWF AIFS (AI) 2.6° (-2.1°) 3.4° (-1.8°) 4.5° (+0.1°) 29
ECMWF IFS 2.7° (-2.0°) 3.2° (-1.1°) 4.3° (-0.1°) 29
NOAA GFS 2.7° (-1.0°) 3.0° (-0.8°) 4.1° (+0.5°) 29
UKMO (UK) 2.9° (-2.1°) 2.9° (-1.2°) — 29
GEM (Canada) 3.5° (-2.6°) 3.6° (-1.5°) 3.8° (+0.1°) 29
DWD ICON 3.5° (-2.6°) 3.2° (-1.8°) — 29
NOAA AIGFS (AI) 3.9° (-3.1°) 3.6° (-2.4°) 3.7° (-1.0°) 29

Method, honestly

The Spread's Phoenix point is the Sky Harbor station (PHX), 3.5 mi from downtown, used for both forecasts and verifications. Each forecast is the last one The Spread archived on the day it was made, the forecast the model was showing at the time, not a reconstruction. A day the station did not report is left out. Truth is the thermometer at Sky Harbor (PHX) — 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; consensus products such as the NBM, itself a blend of models, are not scored here. 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.

  • Fri Oct 16 14 days out the models said 88–101; it hit 87. ECMWF led (off 0.2°F).
  • Thu Oct 15 14 days out the models said 82–94; it hit 88. AIFS led (off 0.3°F); GEM ran 2°F cool.
  • Wed Oct 14 14 days out the models said 73–96; it hit 78. GFS led (off 0.3°F); GEM ran 3°F cool.
  • Tue Oct 13 14 days out the models said 91–99; it hit 78. UKMO led (off 0.2°F).
  • Mon Oct 12 14 days out the models said 89–99; it hit 83. GFS led (off 1.1°F); ECMWF ran 7°F cool.
  • Sun Oct 11 14 days out the models said 94–100; it hit 89. ICON led (off 1.8°F); AIGFS ran 5°F cool.
  • Sat Oct 10 14 days out the models said 92–99; it hit 96. GFS led (off 1.3°F); ICON ran 8°F cool.
  • Fri Oct 9 14 days out the models said 85–101; it hit 104. ECMWF led (off 2.2°F); ICON ran 5°F cool.
  • Thu Oct 8 14 days out the models said 72–99; it hit 104. ECMWF led (off 0.5°F); AIGFS ran 5°F cool.
  • Wed Oct 7 14 days out the models said 96–104; it hit 102. ECMWF led (off 0.1°F); AIGFS ran 4°F cool.
  • Tue Oct 6 13 days out the models said 94–100; it hit 98. UKMO led (off 0.2°F).
  • Mon Oct 5 14 days out the models said 85–102; it hit 98. ECMWF led (off 0.2°F); AIGFS ran 3°F cool.
  • Sun Oct 4 14 days out the models said 95–102; it hit 99. AIFS led (off 0.0°F); AIGFS ran 4°F cool.
  • Sat Oct 3 14 days out the models said 88–104; it hit 97. AIFS led (off 0.2°F); ICON ran 4°F cool.
  • Fri Oct 2 14 days out the models said 95–100; it hit 97. GFS led (off 0.7°F); ICON ran 4°F cool.
  • Thu Oct 1 14 days out the models said 86–105; it hit 95. GFS led (off 1.9°F); ECMWF ran 9°F cool.
  • Wed Sep 30 14 days out the models said 98–102; it hit 86. GFS led (off 0.3°F); GEM ran 13°F cool.
  • Tue Sep 29 14 days out the models said 97–110; it hit 83. UKMO led (off 0.5°F); GEM ran 10°F cool.
  • Mon Sep 28 14 days out the models said 92–106; it hit 83. ECMWF led (off 0.1°F); GFS ran 9°F warm.
  • Sun Sep 27 14 days out the models said 95–110; it hit 97. ECMWF led (off 0.9°F); UKMO ran 8°F cool.
  • Sat Sep 26 14 days out the models said 89–102; it hit 100. ECMWF led (off 0.6°F); UKMO ran 5°F cool.
  • Fri Sep 25 14 days out the models said 95–102; it hit 95. ICON led (off 0.3°F); UKMO ran 4°F cool.
  • Thu Sep 24 14 days out the models said 87–103; it hit 88. AIFS led (off 0.3°F); GEM ran 9°F warm.
  • Wed Sep 23 14 days out the models said 93–102; it hit 99. ECMWF led (off 1.0°F); AIFS ran 7°F cool.
  • Tue Sep 22 14 days out the models said 99–102; it hit 100. ECMWF led (off 0.2°F); AIGFS ran 5°F cool.
  • Mon Sep 21 14 days out the models said 95–100; it hit 102. UKMO led (off 0.5°F); ICON ran 5°F cool.
  • Sun Sep 20 14 days out the models said 98–102; it hit 104. ECMWF led (off 3.4°F); AIGFS ran 7°F cool.
  • Sat Sep 19 14 days out the models said 97–99; it hit 103. AIFS led (off 2.0°F); UKMO ran 5°F cool.
  • Fri Sep 18 14 days out the models said 97–105; it hit 102. AIFS led (off 1.8°F); UKMO ran 5°F cool.
  • Thu Sep 17 13 days out the models said 96–108; it hit 90. GEM led (off 1.4°F); ECMWF ran 4°F warm.
  • Wed Sep 16 14 days out the models said 99–105; it hit 95. ICON led (off 3.4°F); AIFS ran 10°F cool.
  • Tue Sep 15 14 days out the models said 94–100; it hit 102. UKMO led (off 2.8°F); ICON ran 8°F cool.
  • Mon Sep 14 14 days out the models said 97–106; it hit 105. GEM led (off 3.3°F); AIGFS ran 8°F cool.
  • Sun Sep 13 14 days out the models said 92–99; it hit 105. UKMO led (off 2.0°F); ICON ran 8°F cool.
  • Sat Sep 12 14 days out the models said 82–108; it hit 104. GEM led (off 0.7°F); ICON ran 8°F cool.
  • Fri Sep 11 14 days out the models said 90–100; it hit 106. GEM led (off 1.3°F); AIFS ran 5°F cool.
  • Thu Sep 10 14 days out the models said 94–104; it hit 109. GFS led (off 1.9°F); AIGFS ran 5°F cool.
  • Wed Sep 9 14 days out the models said 96–102; it hit 107. UKMO led (off 0.6°F); AIGFS ran 5°F cool.
  • Tue Sep 8 14 days out the models said 86–104; it hit 108. ICON led (off 0.2°F); AIGFS ran 4°F cool.
  • Mon Sep 7 14 days out the models said 99–108; it hit 106. GFS led (off 0.3°F); UKMO ran 10°F cool.
  • Sun Sep 6 14 days out the models said 94–104; it hit 107. ECMWF led (off 1.5°F); GEM ran 6°F cool.
  • Sat Sep 5 14 days out the models said 101–106; it hit 104. ECMWF led (off 1.6°F); UKMO ran 7°F cool.
  • Fri Sep 4 14 days out the models said 101–105; it hit 104. GFS led (off 1.4°F); ICON ran 8°F cool.
  • Thu Sep 3 14 days out the models said 91–104; it hit 103. ECMWF led (off 1.6°F); UKMO ran 6°F cool.
  • Wed Sep 2 14 days out the models said 98–102; it hit 104. GFS led (off 1.9°F); UKMO ran 6°F cool.
  • Tue Sep 1 13 days out the models said 102–104; it hit 101. GFS led (off 0.0°F); ECMWF ran 7°F cool.
  • Mon Aug 31 12 days out the models said 104–108; it hit 91. UKMO led (off 0.0°F); GFS ran 9°F warm.
  • Sun Aug 30 11 days out the models said 108–112; it hit 106. GFS led (off 0.4°F); AIFS ran 10°F cool.
  • Sat Aug 29 10 days out the models said 108–114; it hit 113. ECMWF led (off 1.9°F); AIFS ran 7°F cool.
  • Fri Aug 28 9 days out the models said 107–115; it hit 112. ICON led (off 0.2°F); GEM ran 7°F cool.
  • Thu Aug 27 8 days out the models said 104–117; it hit 113. ECMWF led (off 0.2°F); GEM ran 4°F cool.
  • Wed Aug 26 7 days out the models said 103–116; it hit 117. ECMWF led (off 0.6°F); GEM ran 6°F cool.
  • Tue Aug 25 6 days out the models said 105–115; it hit 115. ICON led (off 1.6°F); UKMO ran 6°F cool.
  • Mon Aug 24 5 days out the models said 103–112; it hit 108. GFS led (off 0.5°F); GEM ran 8°F cool.
  • Sun Aug 23 4 days out the models said 99–111; it hit 113. ICON led (off 0.4°F); GEM ran 11°F cool.
  • Mon Aug 17 14 days out the models said 95–108; it hit 114. GFS led (off 0.8°F); GEM ran 4°F cool.
  • Sun Aug 16 14 days out the models said 94–103; it hit 109. GFS led (off 0.4°F); UKMO ran 7°F cool.
  • Sat Aug 15 14 days out the models said 86–103; it hit 108. GFS led (off 1.1°F); UKMO ran 4°F cool.
  • Fri Aug 14 14 days out the models said 101–106; it hit 100. ICON led (off 0.1°F); AIFS ran 4°F cool.
  • Thu Aug 13 14 days out the models said 97–103; it hit 97. GEM led (off 0.5°F); ICON ran 7°F cool.
  • Wed Aug 12 14 days out the models said 96–108; it hit 95. AIGFS led (off 0.4°F); GFS ran 7°F warm.
  • Tue Aug 11 14 days out the models said 88–104; it hit 103. AIFS led (off 0.2°F); UKMO ran 3°F warm.
  • Mon Aug 10 14 days out the models said 92–104; it hit 108. ICON led (off 0.0°F); ECMWF ran 4°F cool.
  • Sun Aug 9 14 days out the models said 100–109; it hit 111. GFS led (off 0.2°F); AIGFS ran 3°F cool.
  • Sat Aug 8 13 days out the models said 94–108; it hit 111. GEM led (off 0.9°F); ECMWF ran 4°F warm.
  • Fri Aug 7 12 days out the models said 96–106; it hit 109. AIFS led (off 0.7°F); UKMO ran 3°F warm.
  • Thu Aug 6 11 days out the models said 97–107; it hit 104. ECMWF led (off 0.5°F); UKMO ran 6°F warm.
  • Wed Aug 5 10 days out the models said 103–109; it hit 104. AIFS led (off 1.8°F); GEM ran 4°F warm.
  • Tue Aug 4 9 days out the models said 103–109; it hit 108. GEM led (off 0.1°F); UKMO ran 3°F warm.
  • Mon Aug 3 8 days out the models said 102–115; it hit 114. ECMWF led (off 0.6°F); AIGFS ran 4°F cool.
  • Sun Aug 2 7 days out the models said 110–113; it hit 114. AIFS led (off 1.0°F); UKMO ran 2°F warm.
  • Sat Aug 1 6 days out the models said 111–117; it hit 114. ICON led (off 0.1°F); UKMO ran 2°F warm.
  • Fri Jul 31 5 days out the models said 108–116; it hit 113. GEM led (off 0.3°F); UKMO ran 2°F warm.
  • Thu Jul 30 4 days out the models said 109–114; it hit 113. AIFS led (off 0.0°F); AIGFS ran 3°F cool.

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The Spread — the forecast spread — is in closed beta. These verification pages are public while the rest is gated.