API Storage condition

As per API specification it has to be stored at room temperature. Here my question is it acceptable, to store the material at 15-20 ℃ ?

As per usp room temperature means 20-25degrees temperature excutions allowed from 15-30 degrees hence if u are stored at 15 degrees any time excrusiond happend that is crossed the limit

Yes, If stability performed at 25°C then better to change your storage condition as NMT 25°C