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Which weather model is most accurate in Boston?

Forecast Highs Lows Rain Model accuracy

Boston, Massachusetts · daily high temperature in °C · trailing 30 days, through Fri Oct 16

Every day, The Spread archives what each major weather model predicted for Boston at 1-, 3-, and 7-day leads, then scores those forecasts against the BOS 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 GFS, which has run cool by about 1.27°C at 3-day lead over this window.

Boston'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
GEM (Canada) 0.8° (+0.6°) 1.5° (-0.5°) 3.0° (-1.1°) 29
DWD ICON 0.9° (-0.2°) 1.2° (-0.2°) — 29
NOAA AIGFS (AI) 1.1° (-0.5°) 1.7° (-0.7°) 2.6° (-0.4°) 29
ECMWF AIFS (AI) 1.2° (-0.8°) 1.2° (-0.9°) 2.9° (-0.8°) 29
ECMWF IFS 1.2° (-0.8°) 1.8° (-0.6°) 2.7° (-1.7°) 29
UKMO (UK) 1.2° (-0.1°) 1.9° (-0.4°) — 29
NOAA GFS 1.5° (-1.2°) 1.7° (-1.3°) 3.0° (-2.4°) 29

Method, honestly

The Spread's Boston point is the Logan station (BOS), 4.1 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 Logan (BOS) — 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 17–19; it hit 21. ECMWF led (off 0.0°C); GFS ran 2°C cool.
  • Thu Oct 15 14 days out the models said 11–24; it hit 17. GEM led (off 0.1°C).
  • Wed Oct 14 14 days out the models said 14–20; it hit 25. AIGFS led (off 0.3°C); AIFS ran 3°C cool.
  • Tue Oct 13 14 days out the models said 13–21; it hit 17. ICON led (off 0.1°C); UKMO ran 2°C warm.
  • Mon Oct 12 14 days out the models said 13–18; it hit 22. GEM led (off 0.8°C); AIFS ran 3°C cool.
  • Sun Oct 11 14 days out the models said 12–15; it hit 16. ECMWF led (off 0.2°C); UKMO ran 2°C warm.
  • Sat Oct 10 14 days out the models said 11–20; it hit 17. ICON led (off 0.2°C); GEM ran 1°C warm.
  • Fri Oct 9 14 days out the models said 16–18; it hit 21. GEM led (off 0.1°C); UKMO ran 2°C cool.
  • Thu Oct 8 14 days out the models said 12–19; it hit 23. ICON led (off 0.1°C); ECMWF ran 1°C cool.
  • Wed Oct 7 14 days out the models said 14–20; it hit 19. UKMO led (off 0.1°C); ECMWF ran 2°C cool.
  • Tue Oct 6 13 days out the models said 14–21; it hit 17. ICON led (off 1.2°C); UKMO ran 3°C cool.
  • Mon Oct 5 14 days out the models said 16–24; it hit 22. GEM led (off 0.3°C); UKMO ran 2°C cool.
  • Sun Oct 4 14 days out the models said 15–23; it hit 17. ICON led (off 0.2°C).
  • Sat Oct 3 14 days out the models said 14–23; it hit 19. ICON led (off 0.2°C); UKMO ran 2°C warm.
  • Fri Oct 2 14 days out the models said 19–23; it hit 31. GEM led (off 0.5°C); GFS ran 4°C cool.
  • Thu Oct 1 14 days out the models said 16–21; it hit 26. UKMO led (off 0.0°C); GFS ran 3°C cool.
  • Wed Sep 30 14 days out the models said 15–23; it hit 19. AIFS led (off 0.3°C); GEM ran 3°C warm.
  • Tue Sep 29 14 days out the models said 19–26; it hit 19. UKMO led (off 0.3°C).
  • Mon Sep 28 14 days out the models said 18–25; it hit 14. GFS led (off 0.2°C); ICON ran 2°C warm.
  • Sun Sep 27 14 days out the models said 19–22; it hit 16. GFS led (off 0.3°C); AIFS ran 1°C warm.
  • Sat Sep 26 14 days out the models said 18–22; it hit 16. ICON led (off 0.3°C); GFS ran 2°C cool.
  • Fri Sep 25 14 days out the models said 15–24; it hit 18. ICON led (off 0.1°C); GFS ran 2°C cool.
  • Thu Sep 24 14 days out the models said 15–21; it hit 18. GEM led (off 0.3°C); GFS ran 3°C cool.
  • Wed Sep 23 14 days out the models said 14–25; it hit 18. GEM led (off 0.2°C); GFS ran 2°C cool.
  • Tue Sep 22 14 days out the models said 18–20; it hit 17. ICON led (off 0.3°C); AIGFS ran 2°C cool.
  • Mon Sep 21 14 days out the models said 18–23; it hit 18. UKMO led (off 0.1°C); ICON ran 1°C warm.
  • Sun Sep 20 14 days out the models said 15–21; it hit 17. ECMWF led (off 0.3°C); AIGFS ran 3°C cool.
  • Sat Sep 19 14 days out the models said 18–24; it hit 17. ECMWF led (off 0.1°C); UKMO ran 1°C warm.
  • Fri Sep 18 14 days out the models said 18–26; it hit 27. AIGFS led (off 0.1°C); AIFS ran 2°C cool.
  • Thu Sep 17 14 days out the models said 19–26; it hit 24. ICON led (off 0.4°C); GEM ran 3°C warm.
  • Wed Sep 16 14 days out the models said 19–26; it hit 27. UKMO led (off 0.4°C); ECMWF ran 4°C cool.
  • Tue Sep 15 14 days out the models said 15–33; it hit 19. AIFS led (off 0.2°C); GFS ran 2°C cool.
  • Mon Sep 14 14 days out the models said 22–26; it hit 23. UKMO led (off 0.2°C); ECMWF ran 2°C cool.
  • Sun Sep 13 14 days out the models said 19–26; it hit 21. ICON led (off 0.1°C); GFS ran 2°C cool.
  • Sat Sep 12 14 days out the models said 16–31; it hit 22. GFS led (off 0.2°C); AIGFS ran 3°C warm.
  • Fri Sep 11 14 days out the models said 22–36; it hit 26. GEM led (off 0.4°C); AIFS ran 2°C cool.
  • Thu Sep 10 14 days out the models said 21–30; it hit 31. GEM led (off 0.2°C); ECMWF ran 2°C cool.
  • Wed Sep 9 14 days out the models said 18–32; it hit 24. AIFS led (off 0.3°C); GEM ran 5°C warm.
  • Tue Sep 8 14 days out the models said 20–26; it hit 27. GEM led (off 0.4°C); UKMO ran 3°C cool.
  • Mon Sep 7 14 days out the models said 23–28; it hit 28. GEM led (off 0.0°C); GFS ran 3°C cool.
  • Sun Sep 6 14 days out the models said 19–26; it hit 20. GFS led (off 0.1°C); GEM ran 2°C warm.
  • Sat Sep 5 14 days out the models said 16–26; it hit 23. GEM led (off 0.4°C); ECMWF ran 2°C cool.
  • Fri Sep 4 14 days out the models said 20–28; it hit 29. ICON led (off 0.8°C); AIFS ran 3°C cool.
  • Thu Sep 3 14 days out the models said 23–26; it hit 23. AIFS led (off 0.7°C); AIGFS ran 4°C warm.
  • Wed Sep 2 14 days out the models said 18–24; it hit 22. UKMO led (off 0.0°C); GEM ran 1°C warm.
  • Tue Sep 1 13 days out the models said 21–30; it hit 21. ICON led (off 0.1°C); UKMO ran 2°C warm.
  • Mon Aug 31 12 days out the models said 26–28; it hit 23. ICON led (off 0.1°C); AIGFS ran 3°C warm.
  • Sun Aug 30 11 days out the models said 23–26; it hit 30. ICON led (off 0.0°C); AIFS ran 2°C cool.
  • Sat Aug 29 10 days out the models said 21–26; it hit 23. GFS led (off 0.6°C); UKMO ran 3°C warm.
  • Fri Aug 28 9 days out the models said 20–29; it hit 28. GEM led (off 0.1°C); ECMWF ran 2°C cool.
  • Thu Aug 27 8 days out the models said 21–29; it hit 29. GEM led (off 0.3°C); AIFS ran 3°C cool.
  • Wed Aug 26 7 days out the models said 25–28; it hit 26. ICON led (off 0.4°C); ECMWF ran 2°C warm.
  • Tue Aug 25 6 days out the models said 24–27; it hit 27. ICON led (off 0.6°C); AIFS ran 2°C cool.
  • Mon Aug 24 5 days out the models said 26–30; it hit 29. GEM led (off 0.8°C); AIFS ran 4°C cool.
  • Sun Aug 23 4 days out the models said 21–29; it hit 22. GEM led (off 0.7°C); UKMO ran 3°C warm.
  • Mon Aug 17 14 days out the models said 23–26; it hit 24. ECMWF led (off 0.1°C); GFS ran 3°C cool.
  • Sun Aug 16 14 days out the models said 22–29; it hit 26. AIFS led (off 0.3°C); GEM ran 2°C warm.
  • Sat Aug 15 14 days out the models said 20–28; it hit 26. AIGFS led (off 0.1°C); ICON ran 2°C warm.
  • Fri Aug 14 14 days out the models said 21–26; it hit 28. ECMWF led (off 0.2°C); GFS ran 1°C warm.
  • Thu Aug 13 14 days out the models said 22–29; it hit 28. GFS led (off 0.3°C); GEM ran 2°C warm.
  • Wed Aug 12 14 days out the models said 22–26; it hit 29. AIGFS led (off 0.1°C); GEM ran 2°C warm.
  • Tue Aug 11 14 days out the models said 26–31; it hit 30. UKMO led (off 0.2°C); AIGFS ran 2°C warm.
  • Mon Aug 10 14 days out the models said 26–31; it hit 29. AIFS led (off 0.3°C); UKMO ran 4°C warm.
  • Sun Aug 9 14 days out the models said 25–33; it hit 33. ICON led (off 0.1°C); AIFS ran 2°C cool.
  • Sat Aug 8 13 days out the models said 24–34; it hit 34. GFS led (off 0.9°C); AIFS ran 4°C cool.
  • Fri Aug 7 12 days out the models said 24–33; it hit 35. GFS led (off 0.7°C); AIFS ran 5°C cool.
  • Thu Aug 6 11 days out the models said 25–32; it hit 32. ICON led (off 0.2°C); AIFS ran 2°C cool.
  • Wed Aug 5 10 days out the models said 26–30; it hit 31. ECMWF led (off 0.1°C); UKMO ran 2°C warm.
  • Tue Aug 4 9 days out the models said 20–30; it hit 29. ECMWF led (off 0.5°C); GFS ran 2°C cool.
  • Mon Aug 3 8 days out the models said 25–29; it hit 25. AIFS led (off 0.7°C); UKMO ran 2°C warm.
  • Sun Aug 2 7 days out the models said 25–30; it hit 29. ECMWF led (off 0.1°C); UKMO ran 2°C warm.
  • Sat Aug 1 6 days out the models said 22–30; it hit 30. ICON led (off 0.2°C); AIFS ran 2°C cool.
  • Fri Jul 31 5 days out the models said 20–26; it hit 25. AIFS led (off 0.1°C); GFS ran 3°C warm.
  • Thu Jul 30 4 days out the models said 19–24; it hit 23. ECMWF led (off 2.2°C); AIGFS ran 4°C cool.

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