I remember when I first got seriously into smoking premium cigars. I read all the magazines, bought a few books and absorbed as much as I could. One thing these sources had in common with regard to cigar storage was that cigars were to be kept in a humidor at an approximate temperature of 70 degrees F? and a relative humidity (RH) of 70%. This is also known as "the 70/70 rule."
Under those conditions, if you can keep your cigars there within a point or two, they will fare quite well. But unless their humidors are kept in climate controlled rooms, most cigar smokers know the reality; in the winter it's too cold; in the summer it's too hot - you get the idea.
Based on my own experience, as well as the trusted word of colleagues and other long-time cigar smokers, keeping your cigars at temperatures around 65° and the humidity at an average RH of around 67% is a good comfort level. Some aficionados keep the RH even lower than that as you'll see shortly.
Moreover, I once read an article about the Davidoff cigar store in London in which the writer said the store has a walk-in humidor solely for vintage cigars that's kept so cold you practically need a winter coat. But you can bet that the humidity in that humidor is perfectly balanced so those rare primos don't lose their finer qualities.
Note that the higher the relative humidity, the softer your cigars will be, which can cause burn problems. When the RH is lower, your cigars will feel a bit firmer. If the RH and temperature are too low, your cigars will eventually lose their moisture and turn into kindling. It's also interesting to note that many cigar smokers who have cigars with thick wrappers, like Maduros for instance, say that they fare better at a lower RH, closer to around 65%. This is most likely due to the higher amount of oils in the wrapper leaf.
As cited above with the London cigar store, there must also be a balance between the temperature and humidity.
Here's something that may help prove the point. I have an old 25-cigar humidor on my office desk. During the summer the average temperature in the box is a pretty constant 75-degrees. Going "by the book," that would appear to be a little high. With a standard small round humidifier in the box the humidity gets up to around 68%. The result is the cigars border on squishy and burn crappy. After removing the humidifier the RH went down to about 62%. That would appear frighteningly low to a lot of cigar smokers, yet the cigars settled down and burned well.
When the RH dipped to 60%, feeling a little paranoid, I put a small Boveda 75% packet in the box to give the RH a boost. (Not one of their regular sized packets. This one was about the size of those wipes you get at the local rib joint.) Within two days, the RH was up to 68% and cigars were all soft again. So, into the trash went the packet and you now see how delicate the conditions can be in some cases. More importantly, it is not healthy to expose your cigars to wide fluctuations in temperature and humidity.
The basic rule for higher and lower than average temperatures is, High temp/Lower RH; Low temp/Higher RH. As for me, I try to keep the temp/humidity balanced at about 68 degrees/67% RH average year round. Eventually you'll find the right mix for your humidor, plus humidors vary too, based on the size of the box, type of humidifier, etc. The key is to find the comfort zone that works best for your cigars.