Days 1-14 are a real forecast from global weather models. Days 15-30 are season-typical values based on climate normals 1991-2020 (MET) — good for planning, NOT an exact forecast that far ahead.
30 days — Alta
14 real + 16 synthesised
Sat · Today Partly cloudy
+7°+4°10%
Sun · Tomorrow Showers
+6°+4°0,5 mm
Monday 7/9 Clear
+9°+3°7%
Tuesday 8/9 Cloudy
+8°+4°1,5 mm
Wednesday 9/9 Clear
+8°+5°9%
Thursday 10/9 Cloudy
+9°+7°17%
Friday 11/9 Cloudy
+9°+7°27%
Saturday 12/9 Cloudy
+9°+7°24%
Sunday 13/9 Cloudy
+12°+8°17%
Monday 14/9 Cloudy
+10°+8°20%
Tuesday 15/9 Cloudy
+10°+8°0,5 mm
Wednesday 16/9 Showers
+9°+6°0,7 mm
Thursday 17/9 Cloudy
+9°+5°3,7 mm
Friday 18/9 Showers
+7°+3°6,6 mm
Saturday 19/9 Rain (climate normal)
+5°-3°8,1 mm
Sunday 20/9 Partly cloudy (climate normal)
+8°-1°20%
Monday 21/9 Partly cloudy (climate normal)
+8°-1°20%
Tuesday 22/9 Rain (climate normal)
+6°-2°6,3 mm
Wednesday 23/9 Partly cloudy (climate normal)
+3°-4°20%
Thursday 24/9 Partly cloudy (climate normal)
+3°-4°20%
Friday 25/9 Rain (climate normal)
+4°-4°7,2 mm
Saturday 26/9 Partly cloudy (climate normal)
+6°-2°20%
Sunday 27/9 Partly cloudy (climate normal)
+7°-2°20%
Monday 28/9 Rain (climate normal)
+9°-1°6,0 mm
Tuesday 29/9 Partly cloudy (climate normal)
+6°-2°20%
Wednesday 30/9 Partly cloudy (climate normal)
+3°-4°20%
Thursday 1/10 Rain (climate normal)
-3°-8°9,8 mm
Friday 2/10 Partly cloudy (climate normal)
-2°-8°20%
Saturday 3/10 Partly cloudy (climate normal)
0°-6°20%
Sunday 4/10 Rain (climate normal)
+2°-5°5,3 mm
How does the long-range forecast work?
Days 1-14: Fetched live from global weather models (ECMWF, GFS) with statistical correction. Reliability about 85 % for days 1-3, about 60 % for days 7-10, about 45 % for days 11-14.
Days 15-30: A real forecast does not exist that far ahead (chaotic system). Instead we show season-typical values: the monthly average Tmax/Tmin from climate normals 1991-2020, with mild weekly variation.
Use: «About how warm is it usually in Oslo the last week of July?» — a good question for days 15-30. «Will it rain on 27 May?» — no serious forecast can answer that.