The reason the love that emanates from the Lord as the sun is experienced as warmth in heaven is that the deeper levels of angels are involved in a love that comes from the divine good, which in turn comes from the Lord. Consequently, their more outward levels, which are warmed by this, are in warmth. This is why warmth and love are mutually responsive to each other in heaven, so that everyone is in the kind of warmth that accords with her or his love, as follows from what we have just been saying.
Our world’s warmth does not enter heaven at all, because it is too crude, being natural and not spiritual. It is different for us, though, since we are in the spiritual world as well as in the natural world. As far as our spirits are concerned, we grow warm exactly according to our loves, but as far as our bodies are concerned, we respond to both—the warmth of our spirits and the warmth of the world. The former flows into the latter, because they correspond.
We can determine the nature of the correspondence of these two kinds of warmth by looking at animals, whose loves—the primary one being for the procreation of offspring of their own species—break forth and become active in response to the presence and touch of warmth from our world’s sun, a warmth that comes primarily in spring and summertime.
People who believe that the inflow of our world’s warmth arouses these loves are much mistaken. There is actually no inflow of what is natural into what is spiritual, but of what is spiritual into what is natural. This latter inflow is of the divine design, while the former would be contrary to the divine design.
from Heaven and Hell, Section 135