I still don't get the Temp/RH thing.

[big ben]

I have been told and referred to a few links here on CW about how RH should be kept constant no matter the temp. I thought I understood it until today.

I have a Vicksburg humidor that is used primarily for aging, so it only gets opened once every few weeks. I do keep a constant eye on the hygrometer through the top glass so that it stays at 62 percent and it stays spot on. If it drops to 60, I add a few drops to the beads and the next day its back on perfect.
Yesterday it read 72 degrees and 62 RH.
Today a cold front came through and the temp dropped to 61 degrees. By far the coldest this humi has ever seen. Guess what the RH was...67 percent! How the heck could that happen overnight when this baby hasn't fluctuated 3 percent all summer?

I looked up the definition for RH again, "The ratio of the amount of water vapor actually in the air compared to the amount of water vapor the air can hold at that particular temperature."

Can someone set me straight again? I saw it with my own eyes that temp most definitely affects RH.
Are you saying that I should lower my RH 5 points when the temp is 61?
I know this is probably beating a dead horse for some of you, but I seriously don't understand.

Mark