Seymour Mountain stands within the watershed of the Raquette River, which drains into the Saint Lawrence River in Canada, and into the Gulf of Saint Lawrence.
The east and southeast slopes of Seymour Mtn. drain via various brooks into the Cold River, a tributary of the Raquette River.
The west side of Seymour Mtn. drains into Seward Brook, thence into the Cold River.
The northern slopes of Seymour drain into Ward Brook, thence into Ampersand Lake, Ampersand Brook, Stony Creek, and the Raquette River.
^Russell M. L. Carson records that Professor A. Guyot and Ernest Sandoz ascended either Seward Mountain or Seymour Mountain in 1870, but it is not clear which.[4]
