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 — Fredrikstad
14 real + 16 synthesised
Tue · Today Partly cloudy
+19°+14°0,4 mm
Wed · Tomorrow Showers
+20°+15°3,8 mm
Thursday 6/8 Showers
+19°+16°3,0 mm
Friday 7/8 Partly cloudy
+19°+12°10%
Saturday 8/8 Clear
+18°+12°2,4 mm
Sunday 9/8 Clear
+20°+13°8%
Monday 10/8 Clear
+20°+11°4%
Tuesday 11/8 Clear
+21°+11°4%
Wednesday 12/8 Partly cloudy
+19°+15°13%
Thursday 13/8 Cloudy
+20°+15°0,5 mm
Friday 14/8 Light rain
+18°+15°9,2 mm
Saturday 15/8 Partly cloudy
+21°+15°11%
Sunday 16/8 Clear
+23°+13°4%
Monday 17/8 Clear
+20°+15°3,1 mm
Tuesday 18/8 Rain (climate normal)
+20°+11°8,0 mm
Wednesday 19/8 Partly cloudy (climate normal)
+23°+13°20%
Thursday 20/8 Partly cloudy (climate normal)
+22°+12°20%
Friday 21/8 Rain (climate normal)
+21°+12°6,2 mm
Saturday 22/8 Partly cloudy (climate normal)
+20°+12°20%
Sunday 23/8 Partly cloudy (climate normal)
+18°+10°20%
Monday 24/8 Rain (climate normal)
+17°+10°4,5 mm
Tuesday 25/8 Partly cloudy (climate normal)
+20°+11°20%
Wednesday 26/8 Partly cloudy (climate normal)
+22°+12°20%
Thursday 27/8 Rain (climate normal)
+23°+13°4,7 mm
Friday 28/8 Partly cloudy (climate normal)
+21°+12°20%
Saturday 29/8 Partly cloudy (climate normal)
+19°+10°20%
Sunday 30/8 Rain (climate normal)
+17°+10°11,3 mm
Monday 31/8 Partly cloudy (climate normal)
+17°+10°20%
Tuesday 1/9 Partly cloudy (climate normal)
+15°+7°20%
Wednesday 2/9 Rain (climate normal)
+18°+9°9,3 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.