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.
The forecast for Trondheim and the places around it comes from the same weather models as the place pages. Radar: RainViewer, images from the last two hours.
30 days — Trondheim
14 real + 16 synthesised
Sat · Today Cloudy
+12°+10°0,2 mm
Sun · Tomorrow Showers
+11°+9°3,5 mm
Monday 5/10 Drizzle
+13°+9°7,8 mm
Tuesday 6/10 Showers
+11°+9°2,0 mm
Wednesday 7/10 Light rain
+9°+7°15,0 mm
Thursday 8/10 Showers
+8°+6°2,1 mm
Friday 9/10 Cloudy
+9°+5°0,2 mm
Saturday 10/10 Cloudy
+9°+6°16%
Sunday 11/10 Cloudy
+8°+5°7,4 mm
Monday 12/10 Showers
+8°+5°6,0 mm
Tuesday 13/10 Cloudy
+7°+2°13%
Wednesday 14/10 Cloudy
+6°+3°8,4 mm
Thursday 15/10 Clear
+7°+5°19%
Friday 16/10 Cloudy
+7°+4°19%
Saturday 17/10 Rain (climate normal)
+7°+2°11,8 mm
Sunday 18/10 Partly cloudy (climate normal)
+9°+4°20%
Monday 19/10 Partly cloudy (climate normal)
+10°+4°20%
Tuesday 20/10 Rain (climate normal)
+8°+3°8,0 mm
Wednesday 21/10 Partly cloudy (climate normal)
+8°+3°20%
Thursday 22/10 Partly cloudy (climate normal)
+6°+2°20%
Friday 23/10 Rain (climate normal)
+7°+2°6,2 mm
Saturday 24/10 Partly cloudy (climate normal)
+10°+4°20%
Sunday 25/10 Partly cloudy (climate normal)
+12°+5°20%
Monday 26/10 Rain (climate normal)
+11°+5°11,8 mm
Tuesday 27/10 Partly cloudy (climate normal)
+11°+5°20%
Wednesday 28/10 Partly cloudy (climate normal)
+7°+2°20%
Thursday 29/10 Rain (climate normal)
+6°+2°12,5 mm
Friday 30/10 Partly cloudy (climate normal)
+7°+2°20%
Saturday 31/10 Partly cloudy (climate normal)
+8°+3°20%
Sunday 1/11 Rain (climate normal)
+4°0°6,7 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.