Forecast accuracy: forecast vs observations

ICON forecast (nearest point, lapse-rate corrected) vs METAR/SYNOP at valid time. MAE — mean absolute error; bias — mean (forecast − observed); ±2° — share within 2 °C. · 2992137 pairs, 7957 stations, since 24.08 17:00 UTC

1 d 3 d 7 d 30 d

Model accuracy — temperature (short range)

Model	MAE T, °C	Bias T	N
DWD NWP 🥇	1.33	-0.12	43963
ECMWF	1.6	-0.46	47724
GFS	1.92	-0.25	47724

Lower MAE = more accurate. Matched METAR/SYNOP, short range; at 3-7 days the ranking usually differs (ECMWF stronger). Updated hourly.

All stations

Lead time	N	MAE T, °C	Bias T	±2°	MAE wind, m/s	MAE P, mmHg
1–6 h	391021	1.2	-0.2	82%	1.2	0.6
7–12 h	390153	1.3	-0.2	80%	1.2	0.7
13–24 h	698221	1.3	-0.2	79%	1.3	0.7
25–48 h	999809	1.4	-0.3	77%	1.3	0.7
49–72 h	467560	1.5	-0.2	74%	1.3	0.8
73–120 h	35681	1.7	-0.4	69%	1.4	0.9

SYNOP stations

Lead time	N	MAE T, °C	Bias T	±2°	MAE wind, m/s	MAE P, mmHg
1–6 h	206433	1.3	-0.3	81%	1.2	0.7
7–12 h	200301	1.3	-0.3	80%	1.2	0.7
13–24 h	349718	1.3	-0.3	79%	1.3	0.7
25–48 h	493716	1.4	-0.4	77%	1.3	0.8
49–72 h	220777	1.5	-0.4	74%	1.3	0.8
73–120 h	14263	1.7	-0.5	68%	1.4	0.9

Airports (METAR)

Lead time	N	MAE T, °C	Bias T	±2°	MAE wind, m/s	MAE P, mmHg
1–6 h	184588	1.2	-0.2	82%	1.2	0.5
7–12 h	189852	1.3	-0.2	80%	1.3	0.6
13–24 h	348503	1.3	-0.2	80%	1.3	0.6
25–48 h	506093	1.4	-0.2	77%	1.3	0.6
49–72 h	246783	1.5	-0.1	74%	1.4	0.7
73–120 h	21418	1.7	-0.2	69%	1.4	0.8

By country (≤24 h)

Country	N	MAE T	Bias
Andorra	226	5.2	-5.2
Tajikistan	2380	2.9	-2.5
Liechtenstein	542	2.8	-2.7
Haiti	219	2.8	-2.7
Nepal	705	2.5	-2.2
Svalbard and Jan Mayen	541	2.4	-2.3
Bosnia and Herzegovina	3204	2.4	-0.9
Sao Tome and Principe	255	2.3	-2.3
Reunion	807	2.3	-1.6
Albania	951	2.2	-1.3
Namibia	3331	2.1	-1.1
Mali	1407	2.0	+0.1
Aland Islands	1083	2.0	+0.6
Honduras	2935	2.0	-0.9
Belize	379	2.0	+0.3
Turks and Caicos Islands	281	1.9	-1.8
Colombia	13920	1.9	-0.7
Ecuador	3390	1.9	-1.2
Chad	1596	1.9	+0.0
Montenegro	1223	1.8	-1.7

Largest errors (≤24 h)

Station	Country	N	MAE T	Bias
Svobodnyj S31445	Russia	18	14.4	+14.4
Beni-Saf S60518	Algeria	126	14.0	+12.5
Darvaz S38856	Tajikistan	84	13.4	-13.4
Madri-Colmenar S08219	Spain	226	12.8	+12.8
Ishkashim S38957	Tajikistan	91	11.3	-11.3
Turgen S36889	Kazakhstan	84	10.9	+10.9
Izana S60010	Spain	243	10.7	-10.7
Garmsar S40756	Iran	182	10.1	+10.1
Bunji S41518	Pakistan	38	9.9	-9.9
Rushan S38951	Tajikistan	80	9.9	-9.9
Khorog S38954	Tajikistan	87	9.8	-9.8
Chinchorro S85405	Chile	243	8.9	+8.9
Vorogovo S23973	Russia	63	8.8	+8.6
Quetzaltenango S78629	Guatemala	31	8.7	+8.7
Houei-Sai * S48926	Laos	42	8.7	+8.7

Typical causes: mountain/coastal siting, elevation mismatch, nocturnal inversions, urban heat island.