四分律行事鈔資持記 3.627

3.627

The Daśādhyāya-vinaya: In places with much rain, four months are in the open, which is the winter period; eight months are under cover, because rain is plentiful in spring and summer. Where there is little rain, it is the reverse of the former: eight months of winter and spring are in the open, and the four months of summer are under cover.