Fermentation Temperature

• While beer is fermenting, it can be vulnerable to changes in temperature. Yeast that gets too hot can start producing byproducts that will spoil the flavor of the beer. If the temperature begins to exceed 100 degrees Fahrenheit, yeast may even begin to die. If fermenting beer gets too cold, fermentation can be inhibited. During brewing, beer is vulnerable to changes in temperature.

Beer Cellaring

• Once brewing is completed and the beer is in its bottle or keg, it needs to be stored. Beer enthusiasts can be particular about storage temperature, but "Imbibe" magazine recommends that for the best aging, beers should be stored in an area that has a temperature range of 20 degrees F or less, with the ideal temperature being around 55 F, plus or minus five degrees. The ideal situation, therefore, is slightly cooler than room temperature, a range known as "cellar temperature."

Damage From Fluctuations

• Although beer can be harmed by temperature fluctuations, beer expert John Verive advises that this damage is generally only noticeable over a much longer time than the typical beer lover will be storing a bottle. The risk from overexposure to sunlight is much greater, not because of temperature, but because bright light can lead to chemical changes in the beer, damaging the flavor and resulting in the phenomenon of "skunked" beer. For most beers, Verive advises, temperature changes are not a serious problem.

Serving Temperature

• Bartenders sometimes experience problems caused by temperature fluctuations. For instance, warm beer can be foamier than cold beer, which leads to waste in serving. However, many beer enthusiasts reject the idea that beer should be served at low temperatures, arguing that each type of beer has its own ideal serving temperature. Slight changes in this temperature may change the drinking experience slightly, but won't harm the beer significantly.