early spring; beginning of spring
Refers to the early part of spring, roughly from the start of spring (立春) through February and into March. Used in both everyday and literary contexts.
first month of the lunar calendar
Traditional term for the first month of the lunar calendar (roughly February). Now mainly encountered in historical or cultural contexts, such as haiku season words.
Lured by the early spring weather, I went out for a walk.
Even though it's early spring, the wind is still cold.
In the old lunar calendar, 初春 meant the start of the new year.
初春 can mean early spring but often specifically refers to the New Year season, whereas 早春 always means the calendar-early part of spring (roughly Feb–March).
Compound of 初 (first, beginning) and 春 (spring). The reading しょしゅん is the on'yomi of both characters.