The Spread

Was the forecast right for Boston on Thu Aug 6?

Boston, Massachusetts · daily high temperature in °C · forecasts from each model's archived runs, verified against ERA5

10 days out, 4 models put Boston's Thu Aug 6 high anywhere from 23° to 32°; by the final call the field had settled to a median of 32°. ERA5 says the day verified at 32° with 5.8 mm of precipitation — rain.

GEM landed closest, off by 0.1°. AIFS ran 2° cold.

10 days out the models said 23–32; it hit 32. GEM led (off 0.1°C); AIFS ran 2°C cold.
The shareable card for this receipt — what this page looks like pasted into a thread.

What every model said, at every lead

Daily-high calls for Thu Aug 6 as each model's runs approached it — the last archived run per day. NBM and The Spread's own blend are consensus products and stay out of these ranges and rankings; the Boston scoreboard shows them, labelled.

Lead AIFSAIGFSECMWFGEMGFSICONUKMO Range
10d · 2026-07-27 23° 32° 26° — 32° — — 23–32°
9d · 2026-07-28 30° 29° 32° — 28° — — 28–32°
8d · 2026-07-29 30° 27° 29° 31° 32° — — 27–32°
7d · 2026-07-30 27° 26° 30° 31° 27° — — 26–31°
6d · 2026-07-31 29° 35° 27° 30° 24° 20° — 20–35°
5d · 2026-08-01 30° 34° 29° 32° 32° 32° 33° 29–34°
4d · 2026-08-02 30° 34° 31° 31° 31° 32° 34° 30–34°
3d · 2026-08-03 30° 33° 29° 32° 30° 33° 33° 29–33°
2d · 2026-08-04 30° 32° 31° 33° 31° 33° 32° 30–33°
1d · 2026-08-05 30° 33° 32° 34° 32° 33° 31° 30–34°
0d · 2026-08-06 30° 33° 33° 32° 32° 32° 32° 30–33°
actual 32°

Read it honestly

This is one date, not a league table. A model can win a day it deserved to lose; rankings only mean something over a window. For that, see which model has been most accurate in Boston — or every city The Spread scores.

Forecasts are what each model's archived runs said at the time, captured at The Spread's sweep times — never reconstructed after the fact. Truth is ERA5 reanalysis (temperature_2m_max). Archive depth varies by city; receipts exist only for dates the archive watched arrive.