Zephyros was born to the Titans, Astraeus and Eos. In Greek times, he dwelt with Boreas in the Thracian mountains. Like many gods, Zephyros had a share of romantic escapades despite his marriage to either Khloris or Iris, becoming the father of several immortal children. In regards to Khloris, who was a nymph of the Isles of the Blessed, it was said that he gave her dominion over flowers and essentially made her the goddess of flowers. With Iris he had a son, Pothos, the god of romantic longing, desire, and yearning. He also served as an attendant to Aphrodite.
At some point, Zephyros fell in love with a mortal man named Hyacinthus, who he found "quite extraordinary." After finding Hyacinthus with Apollo, playing a game of quoits, Zephyros accidentally killed Hyacinthus in a jealous rage. As the mortal died, Apollo transformed him into a flower, a hyacinth. Aphrodite's immortal son Eros offered Zephyros protection, on the condition that he would work with him forever.
Jason Grace identifies the god as Favonius, his Roman form, while Nico di Angelo identifies the god as Zephyros, his Greek form. Zephyros tells the duo that he does not care if the duo calls him Zephyros or Favonius because the split between Roman and Greek does not affect him, as he is a minor god.
Zephyros is mentioned several times by the Greek god Apollo throughout the book. Apollo states that he regrets blaming Zephyros for Hyacinthus' death. Later in the book, Zephyros swept up the remains of the dryads who had sacrificed their life for Apollo. This led Apollo to conclude that Zephyros had finally forgiven him after centuries of rivalry. He also helped Apollo, who had lost his archery powers, accurately shoot an arrow into the Colossus Neronis' ear.
Zephyros presumably possesses the standard powers of a god.
- Aerokinesis: As the God of the West Wind, Zephyros has divine authority and absolute control over the air, though not as much as Aeolus and Zeus. His jurisdiction over this province enables him to access abilities such as:
- Flight: Zephyros is able to fly by riding air currents.
- Wind Control/Generation: Zephyros is able to generate and control wind.
- Speed: Zephyros is able to move at incredible speeds that are even faster than a god's teleportation.
- Chlorokinesis (limited): As he's the Anemoi of Spring, and in spring the plants grow faster and more healthy, thus he's possibly the responsible for making this. This could be reinforced because he made Khloris the goddess of flowers like Demeter made Triptolemus a minor god of the farm.
- The West Wind was said to be the most favorable of the four.
- Zephyros was said to be the Bringer of the Spring Winds.
- He has close ties with his brother, Boreas, as they both lived together in the time of Ancient Greece.
- He was also called Zephyr.
- The creek that runs through the forest in Camp Half-Blood is named after him.
- He is the wind god that appears in the left-hand side of Botticelli's painting, "The Birth of Venus".
- According to Annabeth Chase, when she was a baby, Zephyros sent her down in a golden cradle to her father by her mother, Athena.
- The spelling of Zephyros's name differs between the two series. In Percy Jackson and the Olympians, his name is spelled Zephyr. In The Heroes of Olympus, his name is spelled Zephyros. It is unknown whether Rick Riordan purposefully decided to change the spelling of the god's name or not.
- If he has a great power over plants (Chlorokinesis) like his brothers has over cold & ice (Boreas) and heat & fire (Notus), the only gods who're above him in that is Gaia, Demeter, Dionysus and Persephone.