Why do plant cells have an additional layer surrounding the cell membrane? What is this layer known as?

As plants cannot move they need protection against variations in temperature, high wind speed, atmospheric moisture, etc. These variations damage the plant cell to an extent of killing them. The cell membrane is a flexible and semi-permeable membrane and cannot fight the adverse climatic changes in its own. Therefore, a stiffer outer covering is present which protects and gives shape to the plant cell. This layer is called the cell wall.