Como dizer "Está pelando (No sentido de estar quente)" em inglês

It would be an adjective.
There are many options, depending on the context. Talking about thing / object / stuff (but not the weather), the first and second examples are better, look:

It's boiling.
It's scalding.
It's scorching.
It's stifling.
And many more... Lol

In addition to those ones, there is also the expression "scalding hot" which would mean (líquido) escaldante [portanto de pelar/pelando], or "fervendo/a ferver".
It´s said mentioning the day temperature when extreme (metaphorical ways) on a hot day, for instance.

The temperature limiting device is installed on tub/shower faucets and is an important safety feature that prevents injuries caused by scalding hot water.

You can also use the adverb "freaking" to emphasize "hot", saying that something is "freaking hot" (está pelando): a freaking hot city/pan, besides what've already been mentioned.

Yup, one more to the table.