It rises in Nemei Lake and flows northward to join Churchill River near Sandy Bay.

[1] The Nemei joins the Churchill downstream from the Island Falls power dam, built in 1929.

The warmest month is July, when the average temperature is 16 °C (61 °F), and the coldest is January, at −22 °C (−8 °F).

These were initially installed too high, emptying above the downstream river level and thus blocking fish passage.

New 3 metres (9.8 ft) tubular culverts were later installed at river level so the fish could swim upstream.