Very hot is subjective. High wattage compact chargers will often get hot. Ideally, they will use components, especially capacitors, that are rated for those temperatures.
If you measure actual temperatures and find them to be above the usual limits for components, then you could contact Framework support & see about a warranty claim.
Has this behavior occurred before or is it just occurring now? Is this the first time you’ve actually touched the charger while it was plugged in before? If it is a lot hotter than before, it could be a hardware issue, otherwise it likely is within what the power supply is rated for.
While I do not have any knowledge of the Framework 13 charger, I can say that when running heavy workloads on my Framework 16 (3D Rendering), the charger sometimes gets so hot you can’t even touch it for more than a few seconds.
The charger likely can get to those temperatures, although of course it definitely isn’t recommended or good for charger longevity.
I would recommend possible putting something to cool it down, such as placing it on a metal surface or even maybe adding an ice pack if you are going to need the constant high performance for a long time. Just make sure no water gets in otherwise both the charger and computer might die.
The Framework chargers are designed similar to other high performance, compact, high density, power adapters. If they are putting out their max capacity they will get quite warm and are designed with the housing reaching temperatures much warmer than the average person thinks is normal.
Just like all modern laptops, components are rated for much higher temperatures over an extended period of time and still expected to function within their design lifetime. Nothing special needs to be done to the power supply other than making sure it can radiate the heat away in an open environment (not covered by a towel, clothing, buried under a book, shut inside a closed box with no ventilation, etc.).
That should be enough to give some idea of the temperature. Might read a little low from actual if the point of contact is small. I’d tape the thermometer sensor down to get firmer contact at least.