About halfway between Racine and Holland, Michigan, sensors keep close tabs on the temperature of Lake Michigan at a depth of 492 feet.
For 30 years, those sensors have reported back almost hourly.
What they say is the depths of Lake Michigan are warming and the annual "turnover" of the lake from warm to cold is changing.
NOAA scientist Craig Stow explains how the lake's seasons have moved.
"What we used to see down at 110 meters used to occur in say November. It's now occurring in January. That season has been pushed back several weeks," Stow said.
The warming isn't likely something you'd feel by sticking your hand in the water, but NOAA says it is significant.
The lake's depths have warmed .11 degrees Fahrenheit per decade for the last 30 years.
In total, a third of a degree.
It's a small change until you realize just how much water is involved.
"It's a whole lot of heat energy," Stow said. "What we're seeing is it's accumulating in the lake over that period of time."
So, what does this mean?
Warmer lake temperatures could wreak havoc on the lake's ecology.
For us on the surface, Stow says a warmer lake could shift our seasons - changing winter in Wisconsin as we know it.
If you've thought Christmas used to be colder around here, you may not just be imagining it.
"Those are all symptoms of a gradual warming that's been happening for a number of decades now," he said.
