What is the normal operating temperature for the MacBook (2016 generation)?

You can find your processor model by entering the following into a terminal:

sysctl -n machdep.cpu.brand_string

which will return a string, for example, like this:

Intel(R) Core(TM) i5-5287U CPU @ 2.90GHz

You can then search for your processor on the intel product specifications page, by pasting for example i5-5287U into the search box.

On the resulting page you will see something called TJUNCTION ...

This is the maximum temperature recommended for that processor. You can monitor this with htop.

Internally, the processor is rated to run up to 100°C and since this model has no blower or fans, that heat will be conducted out to the frame. The nature of conductive heat transfer is that the case itself won't get that hot unless it's insulated to near perfection.

The system will slow down the processor to keep the internal thermal temperatures in line, but most modern cell phones, tablets and computers will get warmer than most people feel is proper and run just fine for extended periods of time. If a store is close, you might make an appointment and have them run diagnostics - just because they are designed to be within the specs - failures can happen on the chips and on the sensors to make yours painfully hot. I would always have someone trained look over something you feel could be a fire risk or dangerous no matter what I say is normal.