The number has never made any sense. They're singing about how it's too hot to do anything and yet it becomes the biggest dance number in the show. The music and the lyrics don't go together...the music does suggest a big dance number, but the lyrics certainly do not. I imagine this was one of those Act II curtain raisers that was put into the show so that the late-comers back from the bar or the rest room haven't actually missed anything important to the storytelling.
But then, very little in KISS ME KATE actually makes any sense, even within their own universe, so...you just have to go with it and enjoy the big dance number, just like you have to just go with everything else in this show for the pleasure of hearing such a brilliant score by one of the masters.