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Why the NorthShore Inline Marathon is in September


If you have heard of the NorthShore Inline Marathon you may ask yourself “Why in the world are they holding an inline marathon in northern Minnesota in September”. If you can believe it this is an extremely common question. We get that question all the time and today we wanted to sit down and talk about the research that went into our special race day.


The history of the NorthShore Inline Marathon races

As a little background on our event. The NorthShore Inline Marathon (NSIM) was founded in 1996 by a group of dedicated inline skaters who wanted to bring a unique and fun event to their home of Duluth. They got to planning and chose the second week of September as their date (originally to avoid the high numbers of tourists in the area during June & July and before the fall colors completely hit the city). Their first year the event had over 1,500 participants and quickly became the largest race in the US. In 2015 NSIM decided to add a few additional races to its weekend adding our St. Lukes Wheels Off Half Marathon, Tunnel 10k run, and our 42k and 21k Rollerski. Recently in 2021 we also added a fun short event for our inline skaters and rollerskiers called the NSIM sprints. Believing in the growth of the industry and fitness all together NSIM has grown from hosting our one event to hosting ten events throughout the weekend of our September date.


So why is it in September?

Since the first event, the NorthShore Inline Marathon has taken place on the second Saturday after Labor Day for (nearly) 26 years. Legend has it that early race organizers did an extensive long-term climate analysis to determine the best conditions of the year for Duluth, Minnesota. Precipitation, wind, sunshine, and temperature were all taken into consideration, and the middle of September was selected as the best bet for fair conditions. The second Saturday after Labor Day was eventually selected as “the day”, and the rest, they say, is history! Only three years weren’t on the second Saturday after Labor day and those were 1998, 2010, and 2020 (due to pandemic). This day has been somewhat of a good luck charm for our race and in its 25 years has only seen a few days have rain usually leaving the course bright and sunny.


NSIM Weather stats:

  • Average start line temperature: 52.8 degrees

  • Coldest start line temperature: 28 degrees in 2007

  • Warmest start line temperature: 72 degrees in 2021

  • Strongest tailwind: 15 mph from the northeast in 2018

  • Strongest headwind: 15 mph from the west-southwest in 2013



The start line of the 2019 NorthShore Inline Marathon.

Race day conditions 1996-2021:

  • Saturday, September 14, 1996 – 7:30am: 44 degrees, cool, with a 10-15mph breeze from the north. Temperatures at the finish at noon were 59 degrees.

  • Saturday, September 13, 1997 – 7:30am: 57 degrees, light overcast skies and a headwind of 7 mph from the south-southwest. Temperatures rose to above 65 degrees at the finish line by noon.

  • Saturday, September 12, 1998 – 9am: 60 degrees, sustained easterly winds of 13 mph.

  • Saturday, September 18, 1999 – 7:40am: 48 degrees, winds around 10 mph from the south-southwest. Finish line temperatures were in the high 60s.

  • Saturday, September 16, 2000 – 7:30am: 44 degrees, 10 mph winds from the southwest. Finish line temperature was 53 degrees.

  • Saturday, September 15, 2001 – 7:30am: 48 degrees, light winds from the north and mostly sunny. Finish line temperature was 60 degrees.

  • Saturday, September 14, 2002 – 7:30am: 53 degrees, westerly winds of 12 mph increasing throughout the day. Finish line temperature was 60 degrees.

  • Saturday, September 13, 2003 – 7:30am: 57 degrees and overcast. Southwest winds of 8mph. Finish line temperature was 65 degrees and 100% humidity

  • Saturday, September 18, 2004 – 7:30am: 57 degrees with a 5mph breeze out of the northeast. Finish line temperature was 62 degrees.

  • Saturday, September 18, 2005 – 7:30am: 48 degrees and calm winds. Finish line temperature was 62 degrees and comfortable.

  • Saturday, September 16, 2006 – 7:30am: 55 degrees and light wind of 5mph from the northeast. There was rain at the start, leaving wet roads for racers. Finish line temperature was 60 degrees.

  • Saturday, September 15, 2007 – 7:30am: 28 degrees and a southwest wind of 9 mph. Temperatures warmed to 40 degrees at the finish line.

  • Saturday, September 13, 2008 – 7:30am: 42 degrees with a 5mph tailwind from the northeast. Finish line temperatures were 62 degrees.

  • Saturday, September 19, 2009 – 7:30am: 56 degrees with a light breeze from the southwest, which picked up throughout the day and shifted to a southwest wind. Finish line temperatures at noon were 73 degrees.

  • Saturday, September 11, 2010 – 7:30am: 58 degrees with a westerly wind of nearly 15 mph. Wind picked up throughout the day, and finish line temperatures were 62 degrees.

  • Saturday, September 17, 2011 – 7:30am: 44 degrees and a headwind of 8 mph from the southwest. At the finish line at noon, wind had increased to nearly 15 mph from the south with a temperature of 55 degrees.

  • Saturday, September 15, 2012 – 9:30am: 58 degrees and a southeast wind of 9 mph, which created a slight crosswind. At the finish line, temperatures rose to 65 degrees by noon.

  • Saturday, September 14, 2013 – 9:30am: 64 degrees and a gusty headwind of 15 mph from the west-southwest. At the finish line, winds tapered off slightly and temperatures were at nearly 70 degrees by noon.

  • Saturday, September 13, 2014 – 9:15am: 52 degrees, with a southwest wind that increased slowly throughout the day. Temperatures held steady for a cool, breezy finish.

  • Saturday, September 19, 2015 – 9:15am: 55 degrees with a west wind of 8 mph. Temperatures increased to 65 degrees by noon at the finish line with a gusty headwind of nearly 15 mph.

  • Saturday, September 17, 2016 – 8:45am: 60 degrees with a west wind of 10 mph. Temperatures at the finish line by noon were 65 degrees and winds had increased to 16 mph from the northwest.

  • Saturday, September 16, 2017 – 8:45am: 64 degrees and calm winds. Intermittent showers and thunderstorms were in the area, and overnight thunderstorms caused the roadway to be wet throughout the race. At the finish line temperatures were 62 degrees with calm wind.

  • Saturday, September 15, 2018 – 8:45am: 65 degrees, cloudy, with a sustained 15 mph tailwind from the northeast. The race course was damp but dried out throughout the day thanks to steadily increasing winds.

  • Saturday, September 14, 2019 – 8:45am: 50 degrees, with a slight westerly wind of 6 mph. At the finish line by 2 pm, the temperature increased to 66 degrees. Plenty of sunshine and dry conditions remained for the entire day.

  • 2020 - Virtual due to the Pandemic | in person canceled

  • Saturday, September 18, 2021, 8:55 am 72 degrees, 18mph wind speeds to the South. At the finish line by 2 pm temperatures increased to 84 degrees, Plenty of sunshine and dry conditions remained for the entire day.


Founded in 1996 by a group of dedicated inline skaters, the NorthShore Inline Marathon (NSIM) quickly grew becoming the world's largest skating race and has had competitors including Olympians professional hockey players, professional speed skaters, and more. NSIM's race is scattered over the beautiful scenic drive in between Duluth and Two Harbours Minnesota on the beautiful shores of Lake Superior. Our race runs close to the same route as the Grandma's Marathon that also takes place in Duluth Minnesota.

Learn more by checking out northshoreinline.com


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