. . . All times I have enjoyed
Greatly, have suffered greatly, both with those
That loved me, and alone; on shore, and when
Through scudding drifters the rainy Hyades
Vext the dim sea. I am become a name;
For always roaming with a hungry heart
Much have I seen and known—cities of men
And manners, climates, councils, governments,
Myself not least, but honored of them all,—
And drunk delight of battle with my peers,
Far on the ringing plains of windy Troy.
Alfred, Lord Tennyson recounts the travels and wisdom of Ulysses. The Norton Anthology of Poetry footnotes "Hyades" with this gloss:
A group of stars in the constellation Taurus, believed to foretell the coming of rain when they rose with the sun.
Now, what is the implication of "believed to foretell"? Suspicious connotations of superstition and mythological mumbo jumbo!
Yet the passage of the constellations through the skies bears a direct causal relation to the seasons—both are correlated with our yearly passage around the sun. Determinations of season and, correspondingly weather, can be made from our position in the cycle through the zodiac. As it happens, the rising and setting of the Hyades corresponds to the rainy seasons in spring and fall, in particular, the notorious rainy season in April.
So, the association between the Hyades and rain is not a mere mythological superstition but a demonstration of reliable calendrical knowledge.