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Which weather model is most accurate in Philadelphia?

Forecast Highs Lows Rain Model accuracy

Philadelphia, Pennsylvania · daily high temperature in °C · 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) (1.11°C); at seven days, too close to call.

The largest standing bias belongs to NOAA AIGFS (AI), which has run cool by about 1.5°C 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 °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) 1.0° (-0.7°) 1.1° (-0.8°) 2.7° (-1.2°) 29
UKMO (UK) 1.1° (-0.8°) 1.5° (-1.1°) — 29
NOAA GFS 1.2° (-0.7°) 1.6° (-0.6°) 2.7° (-1.1°) 29
GEM (Canada) 1.3° (-0.9°) 1.5° (-0.6°) 2.8° (-0.9°) 29
DWD ICON 1.3° (-1.1°) 1.6° (-1.4°) — 29
ECMWF IFS 1.3° (-0.9°) 1.5° (-1.2°) 3.9° (-2.1°) 29
NOAA AIGFS (AI) 1.6° (-1.3°) 1.9° (-1.5°) 2.8° (-1.4°) 29

Method, honestly

The Spread's Philadelphia point is the Philadelphia International station (PHL), 10 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 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 13–22; it hit 25. AIGFS led (off 0.1°C); ECMWF ran 2°C warm.
  • Thu Oct 15 14 days out the models said 14–27; it hit 23. UKMO led (off 0.1°C); AIGFS ran 2°C cool.
  • Wed Oct 14 14 days out the models said 17–23; it hit 27. UKMO led (off 0.5°C); AIFS ran 3°C warm.
  • Tue Oct 13 14 days out the models said 15–26; it hit 27. GFS led (off 0.6°C); GEM ran 4°C cool.
  • Mon Oct 12 14 days out the models said 17–21; it hit 23. UKMO led (off 0.1°C); AIGFS ran 2°C cool.
  • Sun Oct 11 14 days out the models said 14–18; it hit 18. UKMO led (off 0.1°C); GEM ran 1°C warm.
  • Sat Oct 10 14 days out the models said 14–25; it hit 24. GFS led (off 2.0°C); UKMO ran 3°C cool.
  • Fri Oct 9 14 days out the models said 17–21; it hit 24. AIFS led (off 0.3°C); GFS ran 2°C cool.
  • Thu Oct 8 14 days out the models said 14–21; it hit 27. AIFS led (off 0.5°C); GEM ran 4°C cool.
  • Wed Oct 7 14 days out the models said 20–22; it hit 22. GFS led (off 0.8°C); ECMWF ran 3°C cool.
  • Tue Oct 6 13 days out the models said 18–21; it hit 18. AIFS led (off 0.7°C); UKMO ran 2°C cool.
  • Mon Oct 5 14 days out the models said 16–24; it hit 23. AIFS led (off 0.0°C); UKMO ran 2°C cool.
  • Sun Oct 4 14 days out the models said 20–28; it hit 18. GFS led (off 0.1°C); GEM ran 2°C warm.
  • Sat Oct 3 14 days out the models said 15–23; it hit 23. UKMO led (off 0.3°C); AIFS ran 2°C cool.
  • Fri Oct 2 14 days out the models said 21–25; it hit 31. AIFS led (off 0.2°C); GEM ran 4°C cool.
  • Thu Oct 1 14 days out the models said 21–23; it hit 28. AIGFS led (off 0.7°C); ICON ran 2°C cool.
  • Wed Sep 30 14 days out the models said 17–28; it hit 25. AIGFS led (off 0.2°C); UKMO ran 2°C cool.
  • Tue Sep 29 14 days out the models said 22–32; it hit 23. UKMO led (off 0.0°C); ICON ran 1°C cool.
  • Mon Sep 28 14 days out the models said 23–28; it hit 21. UKMO led (off 1.2°C); AIGFS ran 4°C cool.
  • Sun Sep 27 14 days out the models said 20–26; it hit 19. ECMWF led (off 0.9°C); AIGFS ran 4°C cool.
  • Sat Sep 26 14 days out the models said 21–25; it hit 20. GEM led (off 0.2°C); AIGFS ran 3°C cool.
  • Fri Sep 25 14 days out the models said 22–27; it hit 24. AIFS led (off 0.2°C); ICON ran 2°C cool.
  • Thu Sep 24 14 days out the models said 16–25; it hit 20. GFS led (off 0.0°C); ECMWF ran 3°C cool.
  • Wed Sep 23 14 days out the models said 17–28; it hit 21. GEM led (off 0.3°C); GFS ran 2°C cool.
  • Tue Sep 22 14 days out the models said 18–23; it hit 19. GEM led (off 0.1°C); ICON ran 2°C cool.
  • Mon Sep 21 14 days out the models said 22–26; it hit 24. UKMO led (off 0.5°C); AIGFS ran 3°C cool.
  • Sun Sep 20 14 days out the models said 17–23; it hit 26. GFS led (off 0.2°C); ECMWF ran 2°C warm.
  • Sat Sep 19 14 days out the models said 24–28; it hit 26. UKMO led (off 0.3°C); ICON ran 2°C cool.
  • Fri Sep 18 14 days out the models said 23–27; it hit 31. ECMWF led (off 0.2°C); GEM ran 2°C cool.
  • Thu Sep 17 14 days out the models said 22–30; it hit 29. ECMWF led (off 0.1°C); GFS ran 2°C warm.
  • Wed Sep 16 14 days out the models said 29–30; it hit 28. GFS led (off 0.0°C); AIGFS ran 2°C cool.
  • Tue Sep 15 14 days out the models said 20–33; it hit 26. GFS led (off 0.0°C); ECMWF ran 2°C cool.
  • Mon Sep 14 14 days out the models said 27–32; it hit 26. AIFS led (off 0.2°C); ECMWF ran 2°C cool.
  • Sun Sep 13 14 days out the models said 23–32; it hit 29. GFS led (off 0.4°C); GEM ran 2°C cool.
  • Sat Sep 12 14 days out the models said 20–32; it hit 28. GEM led (off 0.1°C); GFS ran 1°C warm.
  • Fri Sep 11 14 days out the models said 24–33; it hit 27. AIGFS led (off 0.2°C); AIFS ran 1°C warm.
  • Thu Sep 10 14 days out the models said 23–34; it hit 32. GFS led (off 0.8°C); ICON ran 4°C cool.
  • Wed Sep 9 14 days out the models said 26–34; it hit 32. GFS led (off 0.2°C); AIGFS ran 2°C cool.
  • Tue Sep 8 14 days out the models said 27–35; it hit 29. ECMWF led (off 0.1°C); AIGFS ran 2°C cool.
  • Mon Sep 7 13 days out the models said 28–35; it hit 28. GFS led (off 0.2°C); AIGFS ran 2°C cool.
  • Sun Sep 6 12 days out the models said 30–36; it hit 28. GEM led (off 0.1°C); AIGFS ran 2°C cool.
  • Sat Sep 5 11 days out the models said 28–37; it hit 29. AIGFS led (off 0.0°C); ECMWF ran 1°C cool.
  • Fri Sep 4 10 days out the models said 27–36; it hit 32. AIGFS led (off 0.2°C); GEM ran 2°C cool.
  • Thu Sep 3 9 days out the models said 28–36; it hit 32. ICON led (off 0.5°C); UKMO ran 3°C warm.
  • Wed Sep 2 8 days out the models said 29–37; it hit 25. AIFS led (off 0.0°C); UKMO ran 3°C warm.
  • Tue Sep 1 7 days out the models said 33–36; it hit 34. UKMO led (off 0.0°C); AIFS ran 4°C cool.
  • Mon Aug 31 6 days out the models said 31–35; it hit 28. AIGFS led (off 0.0°C); UKMO ran 3°C warm.
  • Sun Aug 30 5 days out the models said 30–31; it hit 31. GEM led (off 0.0°C); UKMO ran 1°C cool.
  • Sat Aug 29 4 days out the models said 27–30; it hit 28. GEM led (off 0.0°C); ECMWF ran 1°C cool.
  • Fri Aug 28 3 days out the models said 27–30; it hit 31. GFS led (off 0.4°C); ICON ran 4°C cool.

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