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Which weather model is most accurate in Phoenix?

Forecast Highs Lows Rain Model accuracy

Phoenix, Arizona · daily high temperature in °C · 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 1.74°C 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 °C 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) 1.4° (-1.2°) 1.9° (-1.0°) 2.5° (+0.0°) 29
ECMWF IFS 1.5° (-1.1°) 1.8° (-0.6°) 2.4° (-0.1°) 29
NOAA GFS 1.5° (-0.6°) 1.7° (-0.4°) 2.3° (+0.3°) 29
UKMO (UK) 1.6° (-1.2°) 1.6° (-0.7°) — 29
GEM (Canada) 1.9° (-1.5°) 2.0° (-0.8°) 2.1° (+0.0°) 29
DWD ICON 1.9° (-1.4°) 1.8° (-1.0°) — 29
NOAA AIGFS (AI) 2.2° (-1.7°) 2.0° (-1.3°) 2.1° (-0.5°) 29

Method, honestly

The Spread's Phoenix point is the Sky Harbor station (PHX), 5.7 km 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 31–38; it hit 31. ECMWF led (off 0.1°C).
  • Thu Oct 15 14 days out the models said 28–34; it hit 31. AIFS led (off 0.2°C); GEM ran 1°C cool.
  • Wed Oct 14 14 days out the models said 23–36; it hit 26. GFS led (off 0.2°C); GEM ran 2°C cool.
  • Tue Oct 13 14 days out the models said 33–37; it hit 26. UKMO led (off 0.1°C).
  • Mon Oct 12 14 days out the models said 32–37; it hit 28. GFS led (off 0.6°C); ECMWF ran 4°C cool.
  • Sun Oct 11 14 days out the models said 34–38; it hit 32. ICON led (off 1.0°C); AIGFS ran 3°C cool.
  • Sat Oct 10 14 days out the models said 33–37; it hit 36. GFS led (off 0.7°C); ICON ran 5°C cool.
  • Fri Oct 9 14 days out the models said 30–38; it hit 40. ECMWF led (off 1.2°C); ICON ran 3°C cool.
  • Thu Oct 8 14 days out the models said 22–37; it hit 40. ECMWF led (off 0.3°C); AIGFS ran 3°C cool.
  • Wed Oct 7 14 days out the models said 35–40; it hit 39. ECMWF led (off 0.1°C); AIGFS ran 2°C cool.
  • Tue Oct 6 13 days out the models said 34–38; it hit 37. UKMO led (off 0.1°C).
  • Mon Oct 5 14 days out the models said 30–39; it hit 37. ECMWF led (off 0.1°C); AIGFS ran 1°C cool.
  • Sun Oct 4 14 days out the models said 35–39; it hit 37. AIFS led (off 0.0°C); AIGFS ran 2°C cool.
  • Sat Oct 3 14 days out the models said 31–40; it hit 36. AIFS led (off 0.1°C); ICON ran 2°C cool.
  • Fri Oct 2 14 days out the models said 35–38; it hit 36. GFS led (off 0.4°C); ICON ran 2°C cool.
  • Thu Oct 1 14 days out the models said 30–40; it hit 35. GFS led (off 1.1°C); ECMWF ran 5°C cool.
  • Wed Sep 30 14 days out the models said 37–39; it hit 30. GFS led (off 0.2°C); GEM ran 7°C cool.
  • Tue Sep 29 14 days out the models said 36–44; it hit 28. UKMO led (off 0.3°C); GEM ran 5°C cool.
  • Mon Sep 28 14 days out the models said 33–41; it hit 28. ECMWF led (off 0.1°C); GFS ran 5°C warm.
  • Sun Sep 27 14 days out the models said 35–43; it hit 36. ECMWF led (off 0.5°C); UKMO ran 4°C cool.
  • Sat Sep 26 14 days out the models said 32–39; it hit 38. ECMWF led (off 0.3°C); UKMO ran 3°C cool.
  • Fri Sep 25 14 days out the models said 35–39; it hit 35. ICON led (off 0.2°C); UKMO ran 2°C cool.
  • Thu Sep 24 14 days out the models said 31–39; it hit 31. AIFS led (off 0.2°C); GEM ran 5°C warm.
  • Wed Sep 23 14 days out the models said 34–39; it hit 37. ECMWF led (off 0.6°C); AIFS ran 4°C cool.
  • Tue Sep 22 14 days out the models said 37–39; it hit 38. ECMWF led (off 0.1°C); AIGFS ran 3°C cool.
  • Mon Sep 21 14 days out the models said 35–38; it hit 39. UKMO led (off 0.3°C); ICON ran 3°C cool.
  • Sun Sep 20 14 days out the models said 37–39; it hit 40. ECMWF led (off 1.9°C); AIGFS ran 4°C cool.
  • Sat Sep 19 14 days out the models said 36–37; it hit 39. AIFS led (off 1.1°C); UKMO ran 3°C cool.
  • Fri Sep 18 14 days out the models said 36–41; it hit 39. AIFS led (off 1.0°C); UKMO ran 3°C cool.
  • Thu Sep 17 13 days out the models said 36–42; it hit 32. GEM led (off 0.8°C); ECMWF ran 2°C warm.
  • Wed Sep 16 14 days out the models said 37–41; it hit 35. ICON led (off 1.9°C); AIFS ran 5°C cool.
  • Tue Sep 15 14 days out the models said 34–38; it hit 39. UKMO led (off 1.6°C); ICON ran 4°C cool.
  • Mon Sep 14 14 days out the models said 36–41; it hit 41. GEM led (off 1.8°C); AIGFS ran 5°C cool.
  • Sun Sep 13 14 days out the models said 34–37; it hit 41. UKMO led (off 1.1°C); ICON ran 4°C cool.
  • Sat Sep 12 14 days out the models said 28–42; it hit 40. GEM led (off 0.4°C); ICON ran 4°C cool.
  • Fri Sep 11 14 days out the models said 32–38; it hit 41. GEM led (off 0.7°C); AIFS ran 3°C cool.
  • Thu Sep 10 14 days out the models said 35–40; it hit 43. GFS led (off 1.1°C); AIGFS ran 3°C cool.
  • Wed Sep 9 14 days out the models said 35–39; it hit 42. UKMO led (off 0.3°C); AIGFS ran 3°C cool.
  • Tue Sep 8 14 days out the models said 30–40; it hit 42. ICON led (off 0.1°C); AIGFS ran 2°C cool.
  • Mon Sep 7 14 days out the models said 37–42; it hit 41. GFS led (off 0.2°C); UKMO ran 5°C cool.
  • Sun Sep 6 14 days out the models said 35–40; it hit 42. ECMWF led (off 0.8°C); GEM ran 3°C cool.
  • Sat Sep 5 14 days out the models said 38–41; it hit 40. ECMWF led (off 0.9°C); UKMO ran 4°C cool.
  • Fri Sep 4 14 days out the models said 38–41; it hit 40. GFS led (off 0.8°C); ICON ran 4°C cool.
  • Thu Sep 3 14 days out the models said 33–40; it hit 39. ECMWF led (off 0.9°C); UKMO ran 3°C cool.
  • Wed Sep 2 14 days out the models said 37–39; it hit 40. GFS led (off 1.1°C); UKMO ran 3°C cool.
  • Tue Sep 1 13 days out the models said 39–40; it hit 38. GFS led (off 0.0°C); ECMWF ran 4°C cool.
  • Mon Aug 31 12 days out the models said 40–42; it hit 33. UKMO led (off 0.0°C); GFS ran 5°C warm.
  • Sun Aug 30 11 days out the models said 42–44; it hit 41. GFS led (off 0.2°C); AIFS ran 5°C cool.
  • Sat Aug 29 10 days out the models said 42–46; it hit 45. ECMWF led (off 1.1°C); AIFS ran 4°C cool.
  • Fri Aug 28 9 days out the models said 42–46; it hit 44. ICON led (off 0.1°C); GEM ran 4°C cool.
  • Thu Aug 27 8 days out the models said 40–47; it hit 45. ECMWF led (off 0.1°C); GEM ran 2°C cool.
  • Wed Aug 26 7 days out the models said 40–47; it hit 47. ECMWF led (off 0.3°C); GEM ran 3°C cool.
  • Tue Aug 25 6 days out the models said 40–46; it hit 46. ICON led (off 0.9°C); UKMO ran 3°C cool.
  • Mon Aug 24 5 days out the models said 39–44; it hit 42. GFS led (off 0.3°C); GEM ran 5°C cool.
  • Sun Aug 23 4 days out the models said 37–44; it hit 45. ICON led (off 0.2°C); GEM ran 6°C cool.
  • Mon Aug 17 14 days out the models said 35–42; it hit 45. GFS led (off 0.4°C); GEM ran 2°C cool.
  • Sun Aug 16 14 days out the models said 34–40; it hit 43. GFS led (off 0.2°C); UKMO ran 4°C cool.
  • Sat Aug 15 14 days out the models said 30–40; it hit 42. GFS led (off 0.6°C); UKMO ran 2°C cool.
  • Fri Aug 14 14 days out the models said 38–41; it hit 38. ICON led (off 0.1°C); AIFS ran 2°C cool.
  • Thu Aug 13 14 days out the models said 36–40; it hit 36. GEM led (off 0.3°C); ICON ran 4°C cool.
  • Wed Aug 12 14 days out the models said 36–42; it hit 35. AIGFS led (off 0.2°C); GFS ran 4°C warm.
  • Tue Aug 11 14 days out the models said 31–40; it hit 39. AIFS led (off 0.1°C); UKMO ran 1°C warm.
  • Mon Aug 10 14 days out the models said 33–40; it hit 42. ICON led (off 0.0°C); ECMWF ran 2°C cool.
  • Sun Aug 9 14 days out the models said 38–43; it hit 44. GFS led (off 0.1°C); AIGFS ran 1°C cool.
  • Sat Aug 8 13 days out the models said 35–42; it hit 44. GEM led (off 0.5°C); ECMWF ran 2°C warm.
  • Fri Aug 7 12 days out the models said 36–41; it hit 43. AIFS led (off 0.4°C); UKMO ran 2°C warm.
  • Thu Aug 6 11 days out the models said 36–42; it hit 40. ECMWF led (off 0.3°C); UKMO ran 3°C warm.
  • Wed Aug 5 10 days out the models said 39–43; it hit 40. AIFS led (off 1.0°C); GEM ran 2°C warm.
  • Tue Aug 4 9 days out the models said 40–43; it hit 42. GEM led (off 0.1°C); UKMO ran 2°C warm.
  • Mon Aug 3 8 days out the models said 39–46; it hit 46. ECMWF led (off 0.3°C); AIGFS ran 2°C cool.
  • Sun Aug 2 7 days out the models said 43–45; it hit 46. AIFS led (off 0.6°C); UKMO ran 1°C warm.
  • Sat Aug 1 6 days out the models said 44–47; it hit 46. ICON led (off 0.1°C); UKMO ran 1°C warm.
  • Fri Jul 31 5 days out the models said 42–47; it hit 45. GEM led (off 0.2°C); UKMO ran 1°C warm.
  • Thu Jul 30 4 days out the models said 43–46; it hit 45. AIFS led (off 0.0°C); AIGFS ran 2°C cool.

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