Why do Jews celebrate Passover in the spring?
Jews celebrate Passover in the spring because the original Passover occurred then, when the death angel passed over Israelite homes marked with the blood of the lamb. The context notes it is associated with the Spring Equinox, unlike Atonement or Yom Kippur, which falls in the fall.
Les explains that the Passover began with the final plague in Egypt, the death of the firstborn. Israel had an out by faith: if they put the blood of the Passover lamb on the doorposts and stayed within the safety of their home, the death angel would pass over. This is what Jews still celebrate today in the Spring of the Year. Les emphasizes that Passover and Atonement are two totally different Feast Days: Passover is in the Spring, associated with the Spring Equinox, while Atonement or Yom Kippur is in the Fall. Christ is our Passover, and the Passover aspect is the protection given by the blood of the Lamb.