IPA: /ˈreɪnɪli/
KK: /ˈreɪnɪli/
In a manner that is characterized by rain or wet weather.
The picnic was canceled because it was raining rainily all day.
Rainily → It is formed from "rain" (from Old English *regn*, meaning water droplets falling from the sky) and "-ily" (a suffix used to form adverbs meaning in a manner of). The word "rainily" means in a manner characterized by rain or rainy conditions.
Think of the word 'rain' and remember that 'rainily' describes how something is done in a rainy manner.