Book One of the Psalms, parallel with the spring season, focuses on the Messianic prophecies, revealing God's plan to redeem Israel by crushing Satan.
The Hebrew word used to mark appointed times connotes a pilgrimage. The Hebrew year contained five steps or seasons, corresponding to God's holy times.
Winter is a time of cold, darkness, and sadness. As many as 10% of people in northern areas have Seasonal Affective Disorder. The Psalms for winter can help.
God never says the Christian life would be easy or that life would always be fair. Difficulties and tests are given to test our hearts and promote humility.