Daily water levels on each of the Great Lakes, except Lake Superior, increased during December. The level of Lake Superior fell by its average amount, while levels on Lakes Michigan-Huron experienced a small, but welcome, increase. Water levels on lakes Erie and Ontario increased much more than average during December.
Daily water levels on Lake Superior fell 8 cm during December, equal to the average decline for the month. The level of Lakes Michigan-Huron rose 6 cm, instead of falling a few centimetres as it usually does. Daily water levels on lakes Erie and Ontario increased 12 and 18 cm, respectively. On average, these two lakes have increased by just 1 cm in past Decembers during the 1918-2007 period of record.