‘And when much time was spent, and the voyage was now dangerous, because the Fast was now already gone by, Paul admonished them, and said to them, “Sirs, I perceive that the voyage will be with injury and much loss, not only of the lading and the ship, but also of our lives.” '
This voyaging had take more time than they had wished, and they appear also to have had some delay at Fair Havens. Thus the Day of Atonement (the Jewish Fast on the tenth day of Tishri) had passed, and the dangerous season for sailing was on them. In the Mediterranean navigation was considered to be difficult from the middle of September and impossible after the middle of November, due to the limitations of their ships. This would probably be early October. Indeed Paul appears to have had at least a premonition, (he was a fairly experienced traveller), and possibly a word from the Lord (note his ‘I perceive' and his note of confident certainty which go beyond just concern), that to continue the voyage would lead to much loss, not only of the ship and cargo, but also of human lives. Whether he was officially called on to give his opinion, or did so because he received a warning from the Lord we are not told.