Which weather model is most accurate in Phoenix?

Every day, The Spread archives what each major weather model predicted for Phoenix one to seven days ahead, then scores those forecasts against the PHX observations once the day has happened. This page covers the trailing 30 days (2026-09-27 to 2026-10-26), for daily high temperature.

Typical miss (MAE) is the average size of a model's miss, in °F. Lean is a model's bias, its usual tilt. 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.

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. A model leads only where its typical miss beats the next one by 0.4°F or more; under that the two are too close to call, and the page names both. Rankings cover the models themselves; NBM and our own blend are omitted because they average the other models. A rolling 30-day window means these numbers change over time.