20-40% relative humidity should be strived for in your home's environment for your own comfort as well as the stability of your wood. Yes, cabinets spec that, as does wood flooring. If your AC doesn't provide that in summer, then it is either oversized, running at the wrong speed, or you live in a temperate climate where the use of a dehumidifier would be more appropriate.

For their furniture collections museums strive to keep the humidity steady in all seasons. The biggest damage to wood is caused by wide fluctuations in humidity. I would think if you could keep the same humidity year round you should be okay even if the humidity in your home is higher than 20-40%.

Got home and checked. It turns out that 50% was too optimistic. It is actually 65% right now.

AC was serviced not so long ago.

I live in the SE, it is very humid here. I don't think 65% is unusual (but I really hate it being so humid as I grew up in a dry climate).

Who should I check with if this is normal?

We too live in the humid south and run a dehumidifier all the time. It pumps a LOT of water out of our air - several gallons a day. I don't know if you would want to run a separate dehumidifier but for LA (Lower Alabama) we find it really helpful.

In Fl where I live humidity ranges between about 30% on the driest day in the winter to well over 90% in the worst part of the summer. 96% humidity isn't unusual here.

Check wunderground for the stats for your area if you don't know.

Oh, I meant humidity in the house.

The outside humidity is out of control all summer long, cannot breathe!

I have never thought of a dehumidifier. Thanks for the tip!