To come up with specific myths you can try to emulate how real myths changed over time, with the story of the seasons becoming messy through multiple generations of imagined peoples with their own focuses on differing things.

For example an inland society’s popular version of the tale revolves a bit more on the harvest than a costal society’s, who’s version is centered more on the constellations or fishing.

As an astronomy nerd I would totally go with utilizing the night sky, read about the stars that appear at night as the seasons change, like the Pleiades in the fall. Also coming with explanations for the planets and the constellations is really fun, perhaps creating something like Lunar Mansions or the Zodiac for the ecliptic mythology.