为何Is it often rainy in spring in NanJing?用is,而不用does it often rain in spring in NanJing呢,

为何Is it often rainy in spring in NanJing?用is,而不用does it often rain in spring in NanJing呢,
还有,does it often rain in summer不是is it often rainy in summer?咧,请具体回答,顺便问一下,下次在碰到这两种题该选does还是is,3q.