You know frost 霜 shuāng fog, 雾 wù dew, 露 lù thunder, 雷 léi hail, 雹 báo etc, are all natural phenomena related to water vapor in the air. These natural phenomena are best demonstrated by Chinese characters composed of the radical 雨.
Tips:
Upon seeing characters with 雨 on the top, just think of the natural phenomena related to water vapor. These characters are semantic top-phonetic bottom such as 雨 yǔ + 非 fēi ＝ 霏fēi, 雨 yǔ + 厉 lì ＝ 雳 lì.
