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Which weather model is most accurate in Chicago?

Forecast Highs Lows Rain Model accuracy

Chicago, Illinois · daily high temperature in °F · trailing 30 days, through Fri Oct 16

Every day, The Spread archives what each major weather model predicted for Chicago at 1-, 3-, and 7-day leads, then scores those forecasts against the MDW 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, ECMWF AIFS (AI) (4.29°F).

The largest standing bias belongs to ECMWF AIFS (AI), which has run cool by about 1.99°F at 1-day lead over this window.

Chicago'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
DWD ICON 1.9° (-0.5°) 3.0° (-1.0°) — 29
NOAA GFS 1.9° (+0.1°) 3.0° (+0.5°) 6.6° (+0.2°) 29
GEM (Canada) 2.0° (+1.1°) 3.7° (-0.9°) 5.1° (-2.2°) 29
NOAA AIGFS (AI) 2.3° (-1.9°) 2.9° (-0.5°) 6.4° (-0.7°) 29
ECMWF AIFS (AI) 2.5° (-2.0°) 2.9° (-1.9°) 4.3° (-2.6°) 29
UKMO (UK) 3.2° (-1.8°) 3.6° (-0.9°) — 29
ECMWF IFS 3.3° (-1.8°) 3.7° (-1.7°) 5.8° (-2.4°) 29

Method, honestly

The Spread's Chicago point is the Midway station (MDW), 9 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 Midway (MDW) — 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 47–60; it hit 58. AIGFS led (off 0.1°F); ECMWF ran 9°F warm.
  • Thu Oct 15 14 days out the models said 60–78; it hit 66. ICON led (off 0.2°F); GFS ran 4°F cool.
  • Wed Oct 14 14 days out the models said 50–78; it hit 67. AIFS led (off 0.1°F); GEM ran 4°F warm.
  • Tue Oct 13 14 days out the models said 59–66; it hit 79. ECMWF led (off 0.1°F); GEM ran 7°F warm.
  • Mon Oct 12 14 days out the models said 59–77; it hit 88. ICON led (off 0.6°F); ECMWF ran 6°F cool.
  • Sun Oct 11 14 days out the models said 53–64; it hit 78. GEM led (off 0.8°F); AIFS ran 5°F cool.
  • Sat Oct 10 14 days out the models said 57–77; it hit 81. ICON led (off 0.5°F); ECMWF ran 6°F cool.
  • Fri Oct 9 14 days out the models said 64–72; it hit 74. ICON led (off 0.3°F); UKMO ran 7°F cool.
  • Thu Oct 8 14 days out the models said 54–71; it hit 73. GEM led (off 0.3°F); ECMWF ran 5°F cool.
  • Wed Oct 7 14 days out the models said 63–72; it hit 79. AIGFS led (off 0.5°F); AIFS ran 6°F cool.
  • Tue Oct 6 13 days out the models said 65–70; it hit 74. GFS led (off 1.7°F); ECMWF ran 4°F cool.
  • Mon Oct 5 14 days out the models said 55–73; it hit 68. ICON led (off 0.5°F); ECMWF ran 4°F cool.
  • Sun Oct 4 14 days out the models said 60–73; it hit 74. GEM led (off 0.2°F); UKMO ran 5°F cool.
  • Sat Oct 3 14 days out the models said 61–70; it hit 70. GEM led (off 0.3°F); ECMWF ran 4°F cool.
  • Fri Oct 2 14 days out the models said 73–79; it hit 65. AIFS led (off 0.3°F); UKMO ran 3°F cool.
  • Thu Oct 1 14 days out the models said 64–81; it hit 72. ECMWF led (off 0.1°F); GFS ran 4°F cool.
  • Wed Sep 30 14 days out the models said 66–81; it hit 70. UKMO led (off 0.8°F); ICON ran 6°F cool.
  • Tue Sep 29 14 days out the models said 66–79; it hit 80. GEM led (off 0.4°F); AIFS ran 6°F cool.
  • Mon Sep 28 14 days out the models said 66–80; it hit 73. ICON led (off 0.8°F); UKMO ran 3°F cool.
  • Sun Sep 27 13 days out the models said 66–79; it hit 72. GFS led (off 0.2°F); UKMO ran 4°F cool.
  • Sat Sep 26 14 days out the models said 67–83; it hit 68. AIFS led (off 0.4°F); GFS ran 5°F warm.
  • Fri Sep 25 14 days out the models said 63–85; it hit 64. ECMWF led (off 0.3°F); GEM ran 4°F warm.
  • Thu Sep 24 14 days out the models said 62–84; it hit 69. GEM led (off 0.1°F); GFS ran 2°F warm.
  • Wed Sep 23 14 days out the models said 62–84; it hit 65. AIGFS led (off 0.0°F); GEM ran 4°F warm.
  • Tue Sep 22 14 days out the models said 68–73; it hit 64. GFS led (off 1.5°F); AIFS ran 4°F cool.
  • Mon Sep 21 14 days out the models said 69–82; it hit 65. ECMWF led (off 0.2°F); AIGFS ran 4°F cool.
  • Sun Sep 20 14 days out the models said 58–72; it hit 69. ECMWF led (off 0.0°F); UKMO ran 2°F warm.
  • Sat Sep 19 14 days out the models said 61–79; it hit 72. AIFS led (off 0.2°F); ICON ran 7°F warm.
  • Fri Sep 18 14 days out the models said 68–76; it hit 72. ICON led (off 0.2°F); GEM ran 4°F warm.
  • Thu Sep 17 14 days out the models said 66–73; it hit 82. GFS led (off 0.8°F); UKMO ran 11°F cool.
  • Wed Sep 16 14 days out the models said 68–84; it hit 75. ECMWF led (off 1.6°F); GFS ran 4°F cool.
  • Tue Sep 15 14 days out the models said 76–88; it hit 85. ECMWF led (off 1.4°F); AIFS ran 5°F cool.
  • Mon Sep 14 14 days out the models said 71–94; it hit 72. ICON led (off 0.1°F); GFS ran 6°F warm.
  • Sun Sep 13 14 days out the models said 78–92; it hit 75. AIGFS led (off 0.1°F); GEM ran 4°F warm.
  • Sat Sep 12 14 days out the models said 71–84; it hit 88. GFS led (off 1.1°F); AIFS ran 5°F cool.
  • Fri Sep 11 14 days out the models said 75–85; it hit 81. ICON led (off 0.4°F); AIFS ran 4°F cool.
  • Thu Sep 10 14 days out the models said 76–97; it hit 76. ECMWF led (off 0.2°F); GFS ran 5°F warm.
  • Wed Sep 9 14 days out the models said 68–83; it hit 80. UKMO led (off 0.7°F); AIGFS ran 3°F cool.
  • Tue Sep 8 14 days out the models said 74–87; it hit 87. GFS led (off 0.5°F); AIFS ran 6°F cool.
  • Mon Sep 7 14 days out the models said 80–88; it hit 80. UKMO led (off 0.8°F); ECMWF ran 4°F cool.
  • Sun Sep 6 14 days out the models said 76–82; it hit 79. GFS led (off 1.1°F); ECMWF ran 4°F cool.
  • Sat Sep 5 14 days out the models said 72–80; it hit 83. ICON led (off 0.5°F); ECMWF ran 4°F cool.
  • Fri Sep 4 14 days out the models said 69–76; it hit 93. GEM led (off 0.4°F); AIFS ran 5°F cool.
  • Thu Sep 3 14 days out the models said 78–95; it hit 92. ICON led (off 1.0°F); GEM ran 7°F warm.
  • Wed Sep 2 13 days out the models said 74–87; it hit 96. GFS led (off 0.1°F); AIFS ran 5°F cool.
  • Tue Sep 1 12 days out the models said 72–86; it hit 94. ICON led (off 0.1°F); AIFS ran 5°F cool.
  • Mon Aug 31 11 days out the models said 72–88; it hit 91. GEM led (off 0.1°F); AIFS ran 4°F cool.
  • Sun Aug 30 10 days out the models said 66–88; it hit 81. AIFS led (off 0.1°F); UKMO ran 8°F warm.
  • Sat Aug 29 9 days out the models said 70–83; it hit 82. ICON led (off 0.1°F); AIFS ran 3°F cool.
  • Fri Aug 28 8 days out the models said 68–80; it hit 84. GFS led (off 0.3°F); AIFS ran 4°F cool.
  • Thu Aug 27 7 days out the models said 72–85; it hit 81. ECMWF led (off 0.0°F); GFS ran 4°F warm.
  • Wed Aug 26 6 days out the models said 80–85; it hit 85. UKMO led (off 0.2°F); ECMWF ran 4°F cool.
  • Tue Aug 25 5 days out the models said 77–85; it hit 81. GFS led (off 0.0°F); AIFS ran 4°F cool.
  • Mon Aug 24 4 days out the models said 74–83; it hit 79. UKMO led (off 0.8°F); GEM ran 5°F warm.
  • Tue Aug 18 14 days out the models said 75–79; it hit 83. ICON led (off 0.8°F); AIFS ran 5°F cool.
  • Mon Aug 17 14 days out the models said 74–88; it hit 78. GEM led (off 0.1°F); GFS ran 4°F cool.
  • Sun Aug 16 14 days out the models said 72–83; it hit 88. GEM led (off 0.7°F); AIFS ran 6°F cool.
  • Sat Aug 15 14 days out the models said 77–82; it hit 84. UKMO led (off 0.3°F); AIGFS ran 9°F cool.
  • Fri Aug 14 14 days out the models said 66–83; it hit 78. ECMWF led (off 0.4°F); UKMO ran 4°F warm.
  • Thu Aug 13 14 days out the models said 71–83; it hit 79. UKMO led (off 0.5°F); AIFS ran 5°F cool.
  • Wed Aug 12 14 days out the models said 72–81; it hit 83. ICON led (off 0.1°F); GFS ran 6°F cool.
  • Tue Aug 11 14 days out the models said 72–97; it hit 79. ECMWF led (off 0.1°F); AIFS ran 3°F cool.
  • Mon Aug 10 14 days out the models said 78–87; it hit 84. AIGFS led (off 1.9°F); AIFS ran 6°F cool.
  • Sun Aug 9 14 days out the models said 80–94; it hit 78. ICON led (off 1.9°F); GEM ran 13°F warm.
  • Sat Aug 8 13 days out the models said 82–95; it hit 80. AIGFS led (off 0.6°F); UKMO ran 3°F warm.
  • Fri Aug 7 12 days out the models said 77–96; it hit 83. AIGFS led (off 0.0°F); GEM ran 6°F warm.
  • Thu Aug 6 11 days out the models said 74–94; it hit 78. AIFS led (off 1.0°F); GEM ran 4°F cool.
  • Wed Aug 5 10 days out the models said 83–92; it hit 84. UKMO led (off 0.1°F); AIFS ran 8°F cool.
  • Tue Aug 4 9 days out the models said 82–90; it hit 84. ECMWF led (off 0.3°F); GEM ran 6°F warm.
  • Mon Aug 3 8 days out the models said 80–91; it hit 78. GEM led (off 1.1°F); GFS ran 6°F cool.
  • Sun Aug 2 7 days out the models said 74–89; it hit 72. GFS led (off 0.0°F); GEM ran 5°F warm.
  • Sat Aug 1 6 days out the models said 73–88; it hit 72. ECMWF led (off 0.1°F); AIGFS ran 3°F cool.
  • Fri Jul 31 5 days out the models said 76–88; it hit 81. GFS led (off 0.5°F); UKMO ran 3°F warm.
  • Thu Jul 30 4 days out the models said 80–88; it hit 84. AIFS led (off 1.5°F); GFS ran 8°F cool.

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