Most AC adapters we've seen typically stay under 50 C when stressed and rarely do they ever go beyond 60 C. If you own the small 90 W AC adapter that ships with the latest XPS 15 series, however, then you might want to be extra careful about where you position it.
https://www.notebookcheck.net/Careful-the-Dell-XPS-15-9500-AC-adapter-can-get-really-hot-at-up-to-60-C-or-140-F.466958.0.html
Long story short, the adapter gets really hot, like a typical dell.
If you are baking cookies on your dell laptop and the laptop burns out, you can now switch to using the adapter to bake.
I have to say, I've never seen my RB15 adapter (Advanced, 230W) get hotter than 40-45 degrees. With 65+, you guys probably got a one-of-a-kind Antarctica-spec unit.