For us human beings, spiritual warmth is the warmth of life, because as already noted it is essentially love. This love is what fire means in the Word. Heavenly fire means love for the Lord and love for our neighbor, and hellish fire means love for ourselves and love of the world.
Hellish fire or love has the same source as heavenly fire or love, namely heaven’s sun or the Lord. However, it is changed into hellfire by the people who receive it, for all inflow from the spiritual world varies depending on how it is received or depending on the forms into which it flows. The same thing happens with the warmth and light from the world’s sun. Warmth flowing from this source into woods and flower beds produces vegetation and pleasant, soft aromas. The same warmth flowing into manure or carrion produces decay and foul stenches. Similarly light from the same sun on one object produces lovely, charming colors, while on another it produces ugly and unpleasant ones. It is the same with the warmth and light from heaven’s sun, which is love. When that warmth or love flows into good recipients, like good people and spirits or angels, it makes their goodness fertile; whereas when it flows into evil people it has the opposite effect. Their evils either stifle it or distort it. Similarly, when heaven’s light flows into the true perceptions of good will, it yields intelligence and wisdom; but when it flows into malicious distortions, it changes there into insanity and various kinds of illusion. Everything depends on reception.
from Heaven and Hell, Sections 568-569