Seasonal climate variations can make a cigar smoker go crazy with worry about his smokes...
Its the Winter, guys, that drives cigar storage batty. When the temperature outside goes down, so does, almost always, the ambient Relative Humidity. And if its happening outside, then its really happening inside, where your heating system is cooking the already dry air. And, of course, the inside of your humidor is being challenged to its maximum by all that dry air. Oh! What to do???
You can't change the weather. You can't turn the heat off inside your house (not without a, probably feminine, reaction not worth mentioning). But, what you can do is BEEF UP the humidification in your humidor. Actually, its the only thing you can do. Install another humidifier, or throw in a handful more Boveda packs, or if its really bad, put a damp sponge (which you will have to re-humidify every day or so) in there to maintain the proper RH.
Speaking of RH, we all know that 70% RH is our goal, and all of the reasons for it. But, in the winter, when the air is cold and dry, letting it get down to 60%-65% is acceptable. For a short time.
A further answer, especially if you have a large humidor, is to move what you will be smoking soon or regularly to a smaller, thus more RH friendly, box for the time being. When the weather warms, and wets, back up, your big humidor will come back to normal and life will, again, be splendid.
Humidors: The Wintertime