Winter Warming?

With all the complaining about the winter weather this year,  I became curious about trends in winter
weather in my home town.  So here is a plot of the last 100 years, or so, of minimum January temperatures in Grand Forks, North Dakota.  The three black lines are regression quartile fits
and the red line is the mean regression fit.  The mean and median fits both indicate that there is roughly a 0.1  degree F per year warming trend over the entire period -- so 6 degrees F since I was in first grade.   This year the minimum was -30F, so quite bit below the median trend line.