title: dynamic change of background in google charts
body: <p>I use the google chart to represent the temperature trend during the year  (every hour of every day).
  I use an aspx page to extract data from a database where a column contains daily temperature values and the graph is dynamically built using those data.
  A second column contains three possible values (0, 1, 2) to indicate rainfall (2 = absent, 0 present).
  I would like (but I have not succeeded so far) to dynamically change the background of the graph as a function of those values (for example white for value 2, light blue for value 1, blue for value 0).
  Is it possible?</p>