later rain
Compare (Hosea 6:3); (Joel 2:23-32); (Zechariah 12:10).
There is both a physical and spiritual meaning: Rain as of old will be restored to Palestine, but, also, there will be a mighty effusion of the Spirit upon restored Israel.
Related Commentaries of Zechariah 10:1
Zechariah 10:1
1 Ask ye of the LORD rain in the time of the latter rain; so the LORD shall make bright clouds, and give them showers of rain, to every one grass in the field.