The level of Lake Superior made an unusual jump in December thanks to heavy rains, snowfall and unseasonably warm temperatures across the region.
The big lake rose nearly a half-inch in December, a month it usually drops 3 inches.
The lake received its highest water supply for December in 116 years of accurate records, according to the International Lake Superior Board of Control.
Lake Superior now sits 9 inches above its normal Jan. 1 level and 1 inch below the level at this time last year.
The level of lakes Michigan and Huron rose 3 inches in December, a month the lakes usually drop 2 inches. Those lakes now sit 12 inches above their long-term average and 2 inches higher than the Jan. 1 level of 2015.
Duluth received 3.7 inches of rain equivalent in December, more than the usual 2.5 inches, while Marquette received more than double the usual precipitation — 4.87 inches compared to 2.3. The warmer temperatures kept rivers open and caused much of the snow that did fall to melt, pushing more water into the lake that would usually be locked up on shore until spring. The unusually warm December temperatures — with little difference between lake and air temperatures — spurred less-than-usual evaporation and thus less lake-effect snow than usual.
Water levels of the upper lakes generally decline from September to March and then rise from April to August.