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