Is it OK to Let a Beer Get Cold, then Warm, then Cold Again? Will This Cause a Beer to ‘Skunk?’
Many people seem to think that a beer is as sensitive as a $200 bottle of wine. You must store it just so or it will turn. The most frequently stated version of the beer-temperature myth is that if a beer has been chilled, then allowed to become warm, and then gets cold again, etc., it will be ruined and undrinkable. Repeated cooling and rewarming a beer will skunk it.
In reality, letting a cold beer get warm has nothing to do with skunking. Most beer has a limited shelf life and will go stale after a few months to, perhaps, a year, depending on the beer. However, the biggest boogeyman for beer is UV light and the resultant photo-oxidation.
On the other hand, beer isn’t that sensitive to changes in temperature. The truth is, most of the beer your buy was almost certainly once cold. Beer tends to be shipped cold but not all beer is kept in the cooler once it reaches the retail shop. Some is stored and sold at room temperature. This does not harm the beer. Small brewers may not be able to afford the cost of cold shipping, however.
Moving from cold conditions to room-temperature conditions, and back again, is not generally going to significantly affect the taste of a beer. So can you re-refrigerate beer? Yes! Does beer have to stay cold once you chill it? Not really. You can move it from the fridge to room temperature and back again without much trouble. Obviously, you wouldn’t want to do this over and over, but if you have leftover beer that has gone warm, it isn’t wasted. Put it back in the fridge and enjoy it later.
Does Beer Go Bad if It Gets Hot?
While beer is not going to be badly effected by going from cold to warm, extreme heat is definitely bad for beer. So, rather than being the change in temperature, it is just how warm the warm temperature is that matters. If you take a bottled beer out of an iced-down cooler at the beach and set it in the hot sand and sun for hours, the bottle and beer will get very hot. This higher temperature, not to mention the possible exposure to light (depending on the bottle) will greatly speed up oxidative reactions within the beer. The longer the beer is exposed to these high temperatures, the worse the effect will be.
Given the above, it stands to reason that storing beer at cooler temperatures will tend to lengthen its drinkable life. Although simply storing your beer at room temperature until you need to chill it for drinking is perfectly fine, especially if you are going to go through it within a month or two, storing beer in the refrigerator is generally a good idea. Remember that the fridge is both a cold AND a dark place. Failing that, go for a cool and dark place like a lower cabinet, or even somewhere in the basement, assuming your basement tends to stay cooler than the rest of the house.
All this explains why beer tends to be shipped cold. While letting a cold beer warm to room temperature, and then cooling it again, will not significantly impact the flavor of a beer, if beer is shipped without refrigeration, it may be subjected to very high temperatures. Beer sitting in an unrefrigerated truck in the middle of summer will likely become much too warm. It may even spend days sweltering in over-hot conditions. This will shorten the beer’s enjoyable life and could alter the taste by the time it reaches the retail destination.
But, if you think about it, while beer brewed and sold within the United States may remain cold during shipping, all the way to the retailer, beer imported into the United States from Europe or elsewhere is very unlikely to make it here without changing temperature quite a few times, from cold, to warm, to cold, to warm again. Yet, I drink German beers, Japanese beers, Czech beers, etc. that are not skunked all the time. 
Most of us beer drinkers have no need to worry about such things as I’ve discussed here. Our beer will be perfectly fine as long as we are reasonable. Storing your beer on the front porch in direct sunlight is not reasonable. Storing it on the back patio next to the barbecue grill is also not reasonable. Yes, I’ve known people who do this.