The Spread Maps Request an invite

Which weather model is most accurate in Philadelphia?

Forecast Highs Lows Rain Model accuracy

Philadelphia, Pennsylvania · daily high temperature in °F · trailing 30 days, through Fri Oct 16

Every day, The Spread archives what each major weather model predicted for Philadelphia at 1-, 3-, and 7-day leads, then scores those forecasts against the PHL 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, ECMWF AIFS (AI) (1.99°F); at seven days, too close to call.

The largest standing bias belongs to NOAA AIGFS (AI), which has run cool by about 2.7°F at 3-day lead over this window.

Philadelphia'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) 1.9° (-1.3°) 2.0° (-1.5°) 4.8° (-2.1°) 29
UKMO (UK) 1.9° (-1.4°) 2.7° (-1.9°) — 29
NOAA GFS 2.2° (-1.3°) 2.9° (-1.0°) 4.9° (-2.0°) 29
GEM (Canada) 2.3° (-1.7°) 2.7° (-1.1°) 5.1° (-1.6°) 29
DWD ICON 2.4° (-2.0°) 2.9° (-2.5°) — 29
ECMWF IFS 2.4° (-1.5°) 2.7° (-2.2°) 7.0° (-3.9°) 29
NOAA AIGFS (AI) 2.8° (-2.4°) 3.4° (-2.7°) 5.0° (-2.5°) 29

Method, honestly

The Spread's Philadelphia point is the Philadelphia International station (PHL), 6 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 Philadelphia International (PHL) — 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 56–71; it hit 77. AIGFS led (off 0.2°F); ECMWF ran 4°F warm.
  • Thu Oct 15 14 days out the models said 58–81; it hit 73. UKMO led (off 0.1°F); AIGFS ran 4°F cool.
  • Wed Oct 14 14 days out the models said 63–74; it hit 80. UKMO led (off 0.9°F); AIFS ran 6°F warm.
  • Tue Oct 13 14 days out the models said 60–78; it hit 81. GFS led (off 1.1°F); GEM ran 8°F cool.
  • Mon Oct 12 14 days out the models said 63–70; it hit 74. UKMO led (off 0.2°F); AIGFS ran 4°F cool.
  • Sun Oct 11 14 days out the models said 57–64; it hit 65. UKMO led (off 0.1°F); GEM ran 2°F warm.
  • Sat Oct 10 14 days out the models said 57–77; it hit 76. GFS led (off 3.6°F); UKMO ran 6°F cool.
  • Fri Oct 9 14 days out the models said 63–69; it hit 76. AIFS led (off 0.5°F); GFS ran 4°F cool.
  • Thu Oct 8 14 days out the models said 57–69; it hit 80. AIFS led (off 0.9°F); GEM ran 7°F cool.
  • Wed Oct 7 14 days out the models said 67–72; it hit 72. GFS led (off 1.4°F); ECMWF ran 6°F cool.
  • Tue Oct 6 13 days out the models said 64–70; it hit 65. AIFS led (off 1.2°F); UKMO ran 3°F cool.
  • Mon Oct 5 14 days out the models said 60–76; it hit 73. AIFS led (off 0.0°F); UKMO ran 4°F cool.
  • Sun Oct 4 14 days out the models said 68–82; it hit 64. GFS led (off 0.1°F); GEM ran 3°F warm.
  • Sat Oct 3 14 days out the models said 59–73; it hit 73. UKMO led (off 0.5°F); AIFS ran 4°F cool.
  • Fri Oct 2 14 days out the models said 70–78; it hit 87. AIFS led (off 0.3°F); GEM ran 7°F cool.
  • Thu Oct 1 14 days out the models said 69–74; it hit 83. AIGFS led (off 1.3°F); ICON ran 4°F cool.
  • Wed Sep 30 14 days out the models said 62–83; it hit 77. AIGFS led (off 0.3°F); UKMO ran 3°F cool.
  • Tue Sep 29 14 days out the models said 71–90; it hit 74. UKMO led (off 0.0°F); ICON ran 2°F cool.
  • Mon Sep 28 14 days out the models said 73–82; it hit 69. UKMO led (off 2.1°F); AIGFS ran 6°F cool.
  • Sun Sep 27 14 days out the models said 69–78; it hit 67. ECMWF led (off 1.7°F); AIGFS ran 7°F cool.
  • Sat Sep 26 14 days out the models said 70–78; it hit 68. GEM led (off 0.4°F); AIGFS ran 5°F cool.
  • Fri Sep 25 14 days out the models said 71–80; it hit 75. AIFS led (off 0.4°F); ICON ran 4°F cool.
  • Thu Sep 24 14 days out the models said 62–77; it hit 68. GFS led (off 0.0°F); ECMWF ran 5°F cool.
  • Wed Sep 23 14 days out the models said 63–83; it hit 70. GEM led (off 0.6°F); GFS ran 4°F cool.
  • Tue Sep 22 14 days out the models said 64–73; it hit 66. GEM led (off 0.1°F); ICON ran 3°F cool.
  • Mon Sep 21 14 days out the models said 71–79; it hit 75. UKMO led (off 0.9°F); AIGFS ran 5°F cool.
  • Sun Sep 20 14 days out the models said 63–74; it hit 78. GFS led (off 0.4°F); ECMWF ran 4°F warm.
  • Sat Sep 19 14 days out the models said 76–82; it hit 78. UKMO led (off 0.5°F); ICON ran 4°F cool.
  • Fri Sep 18 14 days out the models said 73–81; it hit 87. ECMWF led (off 0.3°F); GEM ran 4°F cool.
  • Thu Sep 17 14 days out the models said 72–87; it hit 84. ECMWF led (off 0.1°F); GFS ran 4°F warm.
  • Wed Sep 16 14 days out the models said 84–87; it hit 83. GFS led (off 0.0°F); AIGFS ran 3°F cool.
  • Tue Sep 15 14 days out the models said 68–92; it hit 79. GFS led (off 0.0°F); ECMWF ran 4°F cool.
  • Mon Sep 14 14 days out the models said 80–89; it hit 78. AIFS led (off 0.4°F); ECMWF ran 4°F cool.
  • Sun Sep 13 14 days out the models said 74–90; it hit 85. GFS led (off 0.7°F); GEM ran 3°F cool.
  • Sat Sep 12 14 days out the models said 68–89; it hit 83. GEM led (off 0.2°F); GFS ran 2°F warm.
  • Fri Sep 11 14 days out the models said 75–92; it hit 81. AIGFS led (off 0.4°F); AIFS ran 2°F warm.
  • Thu Sep 10 14 days out the models said 74–94; it hit 90. GFS led (off 1.4°F); ICON ran 8°F cool.
  • Wed Sep 9 14 days out the models said 80–93; it hit 89. GFS led (off 0.4°F); AIGFS ran 4°F cool.
  • Tue Sep 8 14 days out the models said 81–95; it hit 85. ECMWF led (off 0.2°F); AIGFS ran 3°F cool.
  • Mon Sep 7 13 days out the models said 82–94; it hit 82. GFS led (off 0.3°F); AIGFS ran 3°F cool.
  • Sun Sep 6 12 days out the models said 85–97; it hit 83. GEM led (off 0.1°F); AIGFS ran 4°F cool.
  • Sat Sep 5 11 days out the models said 82–98; it hit 84. AIGFS led (off 0.0°F); ECMWF ran 2°F cool.
  • Fri Sep 4 10 days out the models said 80–97; it hit 89. AIGFS led (off 0.3°F); GEM ran 4°F cool.
  • Thu Sep 3 9 days out the models said 82–96; it hit 89. ICON led (off 0.9°F); UKMO ran 5°F warm.
  • Wed Sep 2 8 days out the models said 84–98; it hit 77. AIFS led (off 0.0°F); UKMO ran 5°F warm.
  • Tue Sep 1 7 days out the models said 92–96; it hit 93. UKMO led (off 0.0°F); AIFS ran 6°F cool.
  • Mon Aug 31 6 days out the models said 87–96; it hit 82. AIGFS led (off 0.0°F); UKMO ran 6°F warm.
  • Sun Aug 30 5 days out the models said 85–88; it hit 87. GEM led (off 0.0°F); UKMO ran 2°F cool.
  • Sat Aug 29 4 days out the models said 81–86; it hit 82. GEM led (off 0.0°F); ECMWF ran 2°F cool.
  • Fri Aug 28 3 days out the models said 80–87; it hit 87. GFS led (off 0.8°F); ICON ran 6°F cool.

Other cities

Atlanta, Georgia Berlin, State of Berlin Boston, Massachusetts Buffalo, New York Charlotte, North Carolina Chicago, Illinois Dallas, Texas Denver, Colorado Detroit, Michigan Houston, Texas London, England Los Angeles, California Miami, Florida Milan, Lombardy Minneapolis, Minnesota New Orleans, Louisiana New York, New York Oklahoma City, Oklahoma Orlando, Florida Paris, Île-de-France Region Phoenix, Arizona Salt Lake City, Utah San Antonio, Texas San Diego, California San Francisco, California Seattle, Washington St. Louis, Missouri Tampa, Florida Washington, District of Columbia

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