What causes grass to turn brown during the summer?

Question: What causes grass to turn brown during the summer?
- Keywords:
  colour,
  grass,
  summer
Asked by sabi123 to Ed, Hayley, Jason, Nathan, Sophie on 14 Mar 2013.
- Edward Bovill answered on 14 Mar 2013:
  
  Grass turns brown during the summer when it gets really, really dry and the grass leaves start to die from lack of water. The root system of the grass is usually still alive at this point (unless it’s been dry for months and months) and a good watering will make the grass turn green again.

Question: What causes grass to turn brown during the summer?