ANSWER:

This is not healthy to drink as it catches a lot of pollution from the air. 

There is no problem in drinking it Isamically if you say bismillah.

QUESTION: We drank rain water which was kept open under the sky after maghrib as we forgot to bring it down from terrace after collecting and now am scared as there is hadith that diseases decree into open vessel on one of the night Plz suggest what can i do now