He had to stick his body against the back of the carriage as the air around him was getting colder. As the carriage moved away from the castle, cold air also started to move, and the freezing wind penetrated the thin nightgown and was enough to make the Crown Princess shiver.
He could only continue to stand at the back of the carriage, and he also had to hold on tightly to the carriage so that he wouldn't accidentally fall to the ground as the vehicle continued to move.
Elennora didn't know where the carriage was going, nor did he know what his mother would do in the middle of the night, but he felt lucky that his mother and the carriage driver didn't notice him.
His mother was sitting in the carriage, and she didn't even notice that her son was following her ever since she was still inside the castle. Sitting in the vehicle, the Queen must have felt warm, and her thick coat would have helped her evade the cold.