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