Temperature is the most important characteristic of fine wine cellaring. Wine should be stored below 20�C and ideally between 14�C and 18�C. Constant temperature is also very important. Daily temperature fluctuations can be more detrimental than storing wine at a higher temperature. As temperature varies, the cork expands and contracts as it heats and cools, causing it to act like a piston and allowing air to enter the bottle. This causes oxidisation of the wine and reduces its life span. Typically air conditioned cellars will achieve temperature stability of approximately 2�C, which is about the best achievable without completely sealing the cellar. Cellars without air conditioning vary depending on the location, but under-house cellars will usually achieve temperature stability of 4-6�C over the average day. Wine cellared inside houses can experience extreme temperature variation, sometimes up to 15�C in one day!
Humidity is the second most important condition to monitor when cellaring wine. An ideal humidity level is between 50-70%. Most wine cellars suffer from lack of humidity (especially air conditioned cellars), which leads to corks drying out, shrinking and eventual wine leakage and oxidisation. Lack of humidity can usually be solved by placing a tray of water on the cellar floor. Too much humidity (>70%) can cause mould to grow on corks which, at its extreme, can destroy a wine. De-humidifiers are readily available to remove and regulate humidity.
A cellar should be as dark as possible. Wine does not like light, as it can cause unwanted reactions to occur in the bottle, sometimes spoiling the wine.