enter link description here http://docs.engineeringtoolbox.com/documents/841/oxygen-solubility-water.png
(source: engineeringtoolbox.com)
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, but I don't know the temperature dependance of the proportionality constant $k_H$--I'll check it out tomorrow and edit it in..