Days 1-14 are a real forecast from global weather models. Days 15-30 are season-typical values based on SMHI climate normals 1991-2020 — good for planning, NOT an exact forecast that far ahead.
30 days — Sundsvall
14 real + 16 synthesised
Thu · Today Fog
+19°+12°3,7 mm
Fri · Tomorrow Partly cloudy
+18°+10°7%
Saturday 8/8 Partly cloudy
+21°+8°6%
Sunday 9/8 Clear
+24°+11°0,2 mm
Monday 10/8 Partly cloudy
+19°+12°0,2 mm
Tuesday 11/8 Clear
+17°+9°5%
Wednesday 12/8 Partly cloudy
+20°+6°7%
Thursday 13/8 Partly cloudy
+26°+10°6%
Friday 14/8 Clear
+20°+12°1,3 mm
Saturday 15/8 Partly cloudy
+19°+10°2,0 mm
Sunday 16/8 Partly cloudy
+15°+10°8,7 mm
Monday 17/8 Fog
+14°+10°3,6 mm
Tuesday 18/8 Clear
+15°+9°4%
Wednesday 19/8 Clear
+18°+4°5%
Thursday 20/8 Rain (climate normal)
+18°+10°5,6 mm
Friday 21/8 Partly cloudy (climate normal)
+20°+12°20%
Saturday 22/8 Partly cloudy (climate normal)
+20°+12°20%
Sunday 23/8 Rain (climate normal)
+20°+12°5,1 mm
Monday 24/8 Partly cloudy (climate normal)
+19°+11°20%
Tuesday 25/8 Partly cloudy (climate normal)
+17°+10°20%
Wednesday 26/8 Rain (climate normal)
+17°+10°7,7 mm
Thursday 27/8 Partly cloudy (climate normal)
+21°+12°20%
Friday 28/8 Partly cloudy (climate normal)
+22°+13°20%
Saturday 29/8 Rain (climate normal)
+22°+13°10,4 mm
Sunday 30/8 Partly cloudy (climate normal)
+21°+12°20%
Monday 31/8 Partly cloudy (climate normal)
+19°+11°20%
Tuesday 1/9 Rain (climate normal)
+11°+5°6,8 mm
Wednesday 2/9 Partly cloudy (climate normal)
+11°+5°20%
Thursday 3/9 Partly cloudy (climate normal)
+14°+7°20%
Friday 4/9 Rain (climate normal)
+15°+8°8,6 mm
How does the long-range forecast work?
Days 1-14: Fetched live from global weather models (ECMWF, GFS) with statistical correction. Reliability ~85% for days 1-3, ~60% for days 7-10, ~45% for days 11-14.
Days 15-30: A real forecast does not exist that far ahead (a chaotic system). Instead we show season-typical values: the month’s average Tmax/Tmin from SMHI climate normals 1991-2020 directly for Sundsvall, with mild weekly variation.
Use: "Roughly how warm is it usually in Stockholm in the last week of July?" — a good question for days 15-30. "Will it rain on 27 May?" — no serious forecast can say.