I was under the impression that "to feel" required a reflexive pronoun to distinguish itself from "to hear". I can guess which one it is through context in this example, but how am I supposed to know the difference in other examples?
word reference says to use reflexive sentirsi means 'perceive self as' .. so perhaps it doesn't apply in this sentence, because here someone is feeling how the weather is. Perhaps.
Yes, you use "sentirsi" to express your own feelings. If you ask someone else to feel, you use "senti" with no reflexive.
This of it as 'to sense' The rest you get from context.
I thought you used fare for temperature - or is that just for hot or cold weather?
You are right, fare is only used with weather.
Senti quanto fa caldo = refers to weather
Senti quanto é caldo = demands to touch something
Would 'quanto caldo e' be wrong?
It can be accepted, but less comon.
why not "you feel how hot it is?"
Because that is indicative and the Italian sentence is imperative.
according to the "conjugate" button, "senti" can mean "you feel" as well as "feel"(imperative).
The Italian sentence is still imperative.
I'm a little confused about why it wouldn't be "Senti come è caldo!"
quanto => how much, come => how, how about.
Just as in a previous examples the "it is" is silent (understood).