Goose Down Sleeping Bag?

So I'm going to Philmont in 3 days. I bought a goose down sleeping bag good to 20 degrees. It is of course a mummy bag. It packs down really nicely. When I went on a shakedown hike a couple weeks ago on the long trail, even my body hear made the bag a little damp (zipper all the way up). So while out in Philmont, if I have the sleeping bag zipper fully open, will that prevent it from getting more moist? Also Vermont has really high humidity, so that may be a contributing factor, I'm not sure.