Here we go, deep musings with the strange nacho person :)
There's a few slightly different interpretations of this quote.
The flowers can symbolize success, satisfaction, or gain.
In the case of success or gain, the rain is a metaphor for struggles or obstacles. The struggles in your life teach you and make you stronger. Once you reach the point you've worked to find, you can look back and see what the problems in your way have taught you and how they've helped you get where you are now. You can use them again to go further still, knowing your flowers were born from the rain.
Alternatively, you can take this quote in terms of personal satisfaction. Your flowers are symbolic for when you realize what exactly you want and need, be it true friendship, love, or a calling in your life, a dedication you are ready to commit to. You wander through the rain as it waters your flowers and you follow them to where you belong. In this case, the rain is not bad, it's a guide and a teacher, however strict. Your rainstorms cultivate the flowers you were meant to have.
