Speak up! Every client is different from the next. While one person may find the room temperature perfect, the very next person may find it too warm or cold. It is important to express your needs verbally in order to get the most out of your session.
It is never a problem to layer another towel on the table, take one off, turn the music down or use more or less pressure. It would be worse to find out after the fact that a client was freezing the whole time and never said anything!