Hello. About a month ago I installed 3 1/2" solid oak in my second story. The sub-floor was covered with felt and I left a 3/4 expansion gap all the way around the room. It was nailed down every 6" with 2" flooring nails. The wood was in my house for two weeks before installing it. There are two areas in the main bedroom that have slightly buckled; I would say they have risen less than 1/4" and both sections are 3-4 feet long. I would take picture but it's really hard to tell by just looking at the areas, but is noticeable if you step on the area. There is no flex while walking on the bucked areas and it feels solid. About two weeks after installation I was out of town for a week and turned my heat down and we had a lot of rain. I'm assuming that the humidity went up because of the lowered heat and rain, I have added a dehumidifier to the upstairs and keeping it at 45% RH. I guess the question is can this problem take care of itself or would the floor need to be pulled up? Right now it's not that obvious but after all that work I hate have any issues and don't want it to get worse this summer as the humidity goes up.

Thats what installers fear most. Your not supposed to do that. Course there could be other issues like what is the thickness of the underlayment you fastend to, was it old funky OSB and or plywood of the correct thickness and of course the rh at time of installation, moisture content of the wood and all that.

What type of a subfloor do you have? Hopefully not particle board. If so that would be your problem. If not, then did you have the boxes of flooring open while letting it acclimate?