Wine is alive, and there are two things which will kill or maim it in no time at all, they are direct sunlight, and temperatures above 25°C (77°F). Even if you are going to drink a wine soon after buying it, beware shops and restaurants where these conditions apply.
Light, aromatic wines are most susceptible, and heavy reds the least.
Sunlight has two harmful properties – ultraviolet light (UV) light, and radiation which heats what it shines on. UV light encourages the breakdown of many chemicals, and the oxidation of others. All this is bad news for the wine. Coloured glass provides some protection.
Temperature. High temperatures cause some chemicals to breakdown, and others to react rapidly. New and unpleasant compounds are also produced.
Avoid rapid changes in temperature as this can cause the cork to move within the bottle, and allow air in. This influx of air causes the wine to go off more quickly.
Ideal storage conditions are:-
Temperature:- 12°C to 13°C (54°F to 56°F).
Humidity:- 60 to 70%. If the cork dries out it will let air into the wine.
Horizontal:- the cork should be in contact with the wine, to prevent it from drying out.
Keep it in the dark. No sources of UV light or heat.