楼主,这个情形“太阳雨”简称为“Sunshower",有时也作”Sun Shower".
此外,为了解释“太阳雨”这个现象,楼主可以有以下几种说法：-
1.Rainy Day In The Sun
2.The Sun Comes Out On A Rainy Day
3.Rain falls while the sun is shining
楼主也可参考以下链接,并见以下的解释：-
"Not found in most dictionaries,the sunshower is a common weather phenomena in which rain falls while the sun is shining outside.This phenomenon is referred to as a “sunshower” in many countries including Canada and the United States."