The figs, as Nietzsche makes clear, are the teachings of Zarathustra (and therefore of Nietzsche himself). A prevalent theme in the Zarathustra, and in much of Nietzsche's work, is that of nihilism, a problem which finally led him to propose a "revaluation of all values". The destruction of values, principles, ways of living, and so on was felt by Nietzsche to result from the prevailing values' own will-to-truth. The values destroy themselves when they turn backwards and discover falsehoods where truth was supposed to dwell.The figs are falling from the trees, they are fine and sweet: and as they fall their red skins split. I am a north wind to ripe figs. Thus, like figs, do these teachings fall to you, my friends: now drink their juice and eat their sweet flesh! It is autumn all around and clear sky and afternoon - Thus Spoke Zarathustra, Part II, "On the Blissful Islands"
As the "north wind" Nietzsche presents himself literally as a force of nature, an icey Hyperborean force descending from Northern Europe to cast the ripened figs to the Earth. The image of a fig is also deeply significant. Note how the figs are already ripe, all Nietzsche can do is take them down off the branches. He cannot create them ex nihilo - they are received, inherited from the past (recall Nietzsche's love of necessity, life overcoming itself, amor fati...) In a passage from Ecce Homo, Nietzsche shares his thoughts about creativity with respect to his experience writing the Zarathustra: "Has anyone at the end of the nineteenth century a distinct conception of what poets of strong ages called inspiration? [...] One is merely incarnation, merely mouthpiece, merely medium of overwhelming forces. [...] One hears, one does not seek; one takes, one does not ask who gives; a thought flashes up like lightning, with necessity, unfalteringly formed - I have never had any choice".
In Twilight of the Idols Nietzsche denounces the notion of free will (and therefore also of blame) as contrary to necessity, sourcing them in the desire to punish those who do you wrong. If there is no free will, the idea goes, those who do us harm cannot be held responsible (and therefore cannot be punished). Elsewhere he speaks of the notion of free will being founded in the idea that we are in essence some sort of separate ego-substrate, a transcendental eye which sees absolutely, and which is not bound by the necessity through which the phenomenal world declares itself. The notion of returning to Earthly values, and of affirming the phenomenal world as the only demonstrable world, is a theme permeating Nietzsche's mature work, and in fact one of the primary themes in the Zarathustra. The old values to be replaced are, after all, those transcendentalising doctrines which interpret life as worthless and which posit other more 'meaningful' worlds, either theistic or metaphysical.
In any case, the metaphor here is poignant - the teachings are just "one necessity more", hanging from the branch, necessitated by the tree, necessitated by the Earth... Necessity itself is not overthrown along with the old values but is in the process of overcoming only affirmed again. And with the wax and wane of the seasons the figs ripen and become ready for harvest. The seasons themselves are a classic example of necessity as life overcoming itself, and as Nietzsche has presented his thought in a clear autumn afternoon, the north wind metaphor is particularly remarkable. His attention to sensations and feelings along with his aversion to merely intellectual argument wholly justifies itself in this vivid display. Autumn signals its fate: the coming of winter - the north wind is a grim reminder of what is to come. But what is so powerful is that Nietzsche saw himself as telling us the history of the next 200 years... a cold and discomforting reminder of the future indeed. He hailed the coming of the new values and therefore also the destruction of the old, a moment of such significance that Nietzsche presents it as nothing less than the murder of God - an act which would plunge Europe into the cold and dark winter of nihilism.
After Zarathustra's disciples take the teachings and begin the creation of new values, nihilism overcomes itself and we emerge refreshed in the Spring and the Summer whence the new values reign, and on again into autumn and to eternal recurrence...