National Weather Service Weather Forecast Office

The record warm March, along with above normal temperatures every other month this year, has led to the warmest start to a year on record at NWS Marquette. Here is a chart displaying the Top 10 warmest starts at NWS Marquette (data back to October 1961) through July 7th: 

Rank	Average Temperature	Year
1	41.3	2012
2	40.0	2010
3	39.9	1987
4	38.7	1998
5	38.5	2006
6	37.4	1990
6	37.4	1991
8	37.2	1999
9	36.6	2001
10	36.5	2000

As you would expect, these warm temperatures have caused Lake Superior temperatures to rise to values normally reached in August and the first part of September (image on the left, below). In the image on the right, you can see the periods of warm weather this year (black line) and how it quickly raised the average Lake Superior temperatures (mid March, early June, and present).

More snow this winter?

The common statement we hear is “The warm Lake Superior temperatures this summer mean that we are going to get a lot of snow this winter”. This statement doesn’t hold true, as the lake temperatures tend to quickly fall back to normal in the fall. This is due to fall storms producing wavy conditions, which causes the lake water to mix and bring cooler water to the surface. Thus, by the time the lake effect snow starts to fly late in the fall, Lake Superior temperatures are back to near normal values. An example of this can be seen in the picture above right. You can see a wide variety of temperatures over the last five years from March through September, but once the fall sets in the variability quickly decreases and is generally within a degree of normal by December.  Using 2010 as an example, it was one of the warmest years on record and had really warm water temperatures, yet we only had 159.6" of snow (about 25" below normal at the time).  This supports the fact that there are several other factors that go into determining how much snow we receive each year. 

One thing that we may see in the late summer and early fall is stronger low pressure systems that feed off the warmer Lake Superior temperatures. Depending on where these storms track, it could lead to stronger winds across Upper Michigan.

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