Forecast error by lead time — all cities
For every night with both a logged forecast and an observation, the error is (forecast − observed) hours. MAE is the mean absolute error (lower = better); bias is the mean signed error (positive = the forecast over-predicts hot hours). “Lead” is how many days ahead the forecast was made (0 = same evening).
| Lead days ahead |
Pairs nights × cities |
MAE hours ≥ 20° | Bias hours ≥ 20° | MAE hours ≥ 25° | Bias hours ≥ 25° |
|---|
Night by night
Observed vs the forecast at 1 day and 3 days ahead. Error shown in brackets; green = within 1 hour, amber = within 3, red = further off. Nights still to come show the current forecast with no observation yet.
| Night | Observed ≥20° / ≥25° |
Forecast 1 day ahead ≥20° / ≥25° (error) |
Forecast 3 days ahead ≥20° / ≥25° (error) |
|---|
How this works
Every time the data updates (about every 3 hours), we record the forecast number of overnight hours at or above 20° and 25° for each upcoming night, tagged by how many days ahead it is. When a night has fully passed (09:00 local), we record what was actually observed. The tables above compare the two.
This measure accumulates. Logging began recently, so there are few completed forecast-vs-observation pairs at first — a night forecast 3 days out only becomes a pair once those 3 days have elapsed. The sample grows daily; come back in a week or two for a well-populated skill table. “Observed” values come from Open-Meteo's recent analysis, the same series that feeds the grey line on the everyday chart, not raw station data.