The Torah does not provide us with the exact weather report for the night of the Covenant. We only know that Avram, exhausted by the visions of God and preparation for the Covenant, falls into a deep slumber at sunset. In Genesis 15:12 the ensuing sensation is described as follows, “As the sun was about to set, a deep sleep fell upon Abram, and a great dark dread descended upon him.”
The primeval man feared the night as a source of unknown and terrifying. The same can be said about Abraham, whose sleep, according to the rabbis, brings forward the prophecies about the future fate of the children of Israel, his descendants.
However, the plain meaning of this verse is of no lesser interest. The sensation, felt by Abraham, is very close to sleep paralysis, a peculiar condition that might be one of the manifestations of post-traumatic stress disorder. In the case of Abraham, this is rather a pre-traumatic experience, since he anticipates all the challenges that our ancestors will have to overcome.
However, this dark and stormy night is illuminated in the end when the flaming torch seals the Covenant, giving Abraham a glimpse of hope. The dread has vanished, the dawn of the new Covenant is about to begin.