We're getting site-finished red oak installed in a house that is also getting many other renovations, and we mentioned that we wanted the wood to acclimate for 1-2 weeks before installation. Our contractor states that we can install it, then paint walls and re-do the bathrooms while it's acclimating (installed), and THEN sand and finish them.

I was under the impression that they should be acclimated before they're laid down. Can someone give me some wisdom?

You are right. Wood flooring is acclimated prior to installation. Allowing it to acclimate after the installation totally defeats the purpose.

if you have an experienced installer he will anticipate the final dimension of the width of the flooring considering the original moisture reading of the flooring and the average humidity of your home. This will work if the wood flooring comes from the factory drier than the homes final wood moisture content.
By keeping less pressure on the sides of the flooring as it is laid there can be tiny gaps between flooring strips. Since wood has a quality of expanding as it gains moisture from acclimating the small gaps will close up before sanding.
It is common to put washers every few rows when installing wide plank which are removed after several rows past where they were used as spacers. The planks will expand as anticipated over time, usually a couple of weeks.
This is possible because wood has a co-efficient of expansion and the gap can be calculated to close with the change of moisture content as it acclimates.
We sometimes spritz the floor with water after it has been laid in anticipation of the flooring gaining moisture content from the humidity in the air, after leaving some little gaps between boards, so as it expands there will not be enough pressure between boards to cause cupping. It is not a guess to leave some gaps.

Ideally you should acclimate the flooring to the midrange of the moisture content (mc) for your area before installing it. That way it won't shrink too much in the drier winter months or expand too much in the more humid summer months. If mc is at the annual average when it gets installed you should be ok. If the mc is below average when it gets installed it might buckle as it takes on moisture......in this case it could be installed with spacers as Pete A. suggests to prevent this problem. If the mc is high when it gets installed it might open gaps as it loses moisture. Year round humidity monitoring and control is important for hardwood flooring.

I'm in NC and we're on day 10 of a near record-breaking stretch of rain. I'm assuming this would affect install for sure. We're installing "standard" red oak, not wide planks. With that in mind, can an expert floor installer still account for the average moisture/humidity, or should I ask my contractor to wait 2 weeks for install?

You can't assume that acclimation will happen in a specific period of time. Acclimation happens based on current mc of wood and the relative humidity of the installation environment.
There are 2 moisture content (mc) charts for NC. What city are you in? Also, does the house have a/c, a heating system, a basement?

Here is what the National Wood Flooring Association had to say about this same issue, back in March:

The summary was that you might be able to cut down acclimation time on the front end, if the readings were within range. On the back end, it was best to give the new install 5 to 7 days of further acclimation before sanding.

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