Although this bon-mot seems to have been generally attributed to Napoleon, I can't find it. I believe you might find it near Bulletin 45 of the Grande Armee in correspondence. Perhaps in a letter to Senate or Josephine.
The general frustration with mud comes out in the account of the passage of the Sona, as well as rationale for the French Army's inability to quickly crush the retreating Russians.
I'm not near my references to check.
One place I believe I read it attributed to Napoleon was the "Panic at Golymin," a short story by Dupont in the Epoque of Cavalry(?)