The only problem with doing that is once it gets to hatch time you have to take that vent plug out again. I leave the plugs out of mine so I don't have fluctuating temps during the hatch, it's easier to keep it steady.
Calibrate the hygrometer. You'll need:
salt
water
zipper storage bag
bowl
Using 2 parts salt to 1 part water, you want to make a 'paste' in the bowl. It should look like wet sand. Put the sand/water mixture bowl inside the storage bag. Place the hygrometer inside the bag (NOT in the bowl). Zip...