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UK Extremes

High Temp
12.5° C
Cromer
Low Temp
-6.3° C
Cairngorm
Precipitation
10.2 mm
Baltasound
Wind Gust
71.5 mph
Cairnwell

Astronomy Forecast for Southampton

Cloud cover, astronomical seeing and atmospheric transparency for the next three days - the conditions that actually decide whether tonight's a good night to get the telescope out.

Forecast run issued 2026-11-12 12:00 UTC • Cached 17:51

Key: ■ Good/Clear   ■ Average/Partly Cloudy   ■ Poor/Cloudy   •   rows shaded blue are evening/overnight hours (20:00-07:00 local).

Thursday 12 November

Time Cloud Cover Seeing Transparency Stability Wind Temp Precip
15:00 6-19% (Clear) 1.25-1.5" (Average) 0.3-0.4 (Good) Stable N Moderate 5°C None
18:00 6-19% (Clear) 1.5-2" (Poor) 0.4-0.5 (Good) Stable N Moderate 2°C None
21:00 0-6% (Clear) 1.5-2" (Poor) 0.4-0.5 (Good) Stable N Light 1°C None

Friday 13 November

Time Cloud Cover Seeing Transparency Stability Wind Temp Precip
00:00 0-6% (Clear) 2-2.5" (Poor) 0.4-0.5 (Good) Stable N Light 0°C None
03:00 0-6% (Clear) 2-2.5" (Poor) 0.4-0.5 (Good) Stable N Light -1°C None
06:00 0-6% (Clear) 2-2.5" (Poor) 0.4-0.5 (Good) Stable N Light -1°C None
09:00 0-6% (Clear) 1.25-1.5" (Average) 0.4-0.5 (Good) Stable N Light 2°C None
12:00 0-6% (Clear) 1-1.25" (Average) 0.3-0.4 (Good) Stable NW Light 6°C None
15:00 0-6% (Clear) 1.25-1.5" (Average) 0.3-0.4 (Good) Stable NW Light 5°C None
18:00 0-6% (Clear) 2-2.5" (Poor) 0.3-0.4 (Good) Stable N Light 2°C None
21:00 6-19% (Clear) 2-2.5" (Poor) 0.4-0.5 (Good) Stable NE Light 1°C None

Saturday 14 November

Time Cloud Cover Seeing Transparency Stability Wind Temp Precip
00:00 6-19% (Clear) 2-2.5" (Poor) 0.4-0.5 (Good) Stable E Light 0°C None
03:00 6-19% (Clear) 2-2.5" (Poor) 0.3-0.4 (Good) Stable SE Light 0°C None
06:00 6-19% (Clear) 2-2.5" (Poor) 0.4-0.5 (Good) Stable E Light 0°C None
09:00 19-31% (Clear) 1.25-1.5" (Average) 0.4-0.5 (Good) Stable E Light 3°C None
12:00 31-44% (Partly Cloudy) 1-1.25" (Average) 0.4-0.5 (Good) Stable S Moderate 9°C None
15:00 44-56% (Partly Cloudy) 1.5-2" (Poor) 0.4-0.5 (Good) Stable S Light 7°C None
18:00 56-69% (Partly Cloudy) 2-2.5" (Poor) 0.4-0.5 (Good) Stable SE Light 4°C None
21:00 94-100% (Cloudy) 1.5-2" (Poor) 0.4-0.5 (Good) Stable SE Light 5°C None

Sunday 15 November

Time Cloud Cover Seeing Transparency Stability Wind Temp Precip
00:00 94-100% (Cloudy) 2-2.5" (Poor) 0.4-0.5 (Good) Stable S Light 4°C None
03:00 69-81% (Cloudy) 1.5-2" (Poor) 0.4-0.5 (Good) Stable S Moderate 5°C None
06:00 81-94% (Cloudy) 1.25-1.5" (Average) >1 (Poor) Stable S Moderate 9°C None
09:00 94-100% (Cloudy) 1.25-1.5" (Average) >1 (Poor) Stable SW Moderate 9°C Rain
12:00 94-100% (Cloudy) 1.25-1.5" (Average) 0.5-0.6 (Average) Slightly Unstable SW Moderate 11°C Rain

Reading It

Cloud cover is the obvious one - no point setting up if it's a solid grey sky. But two clear nights can still look very different through a telescope, which is where the other two columns matter:

Astronomical seeing measures how steady the air is, in arcseconds - turbulence in the atmosphere is what makes stars twinkle and blurs fine detail on planets and the Moon, even under a perfectly clear sky. Smaller numbers are better (under 1" is good, over 2" means the image will visibly shimmer).

Atmospheric transparency measures how much starlight is lost to haze, thin high cloud or dust that isn't necessarily obvious to the naked eye - given in magnitudes lost per air mass. Smaller numbers mean a clearer, darker sky, which matters most for faint targets like galaxies and nebulae rather than bright ones like the Moon or planets.

Stability (the atmosphere's "lifted index") flags a raised risk of thunderstorms or sudden cloud building when marked Unstable, regardless of what the cloud forecast says right now.

See also: Sun, Earth & Moon • Night Sky Viewer • Sun Position • Meteor Shower Calendar

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