![enter link description here][1]

The graph(blue lines are what you want) only goes till $50^o C$, but we can extrapolate and say that the oxygen level will become a fifth or so by the time the water reaches its boiling point.

The solubility comes from [Henry's law][2], but I don't know the temperature dependance of the proportionality constant $k_H$--I'll check it out tomorrow and edit it in..

  [1]: http://docs.engineeringtoolbox.com/documents/841/oxygen-solubility-water.png
  [2]: http://enwp.org/Henry's_law