Grandma’s Marathon benefits from the truth about Lake Superior: It’s cooler by the lake

DULUTH - Luck is one reason for the remarkable running weather at Grandma’s Marathon the past 48 years.

Lake Superior gets most of the credit, but luck is an ingredient.

Go back just one year. Heavy rain was forecast along the North Shore, yet there was only light rain and 50-degree temperatures on race day — nearly perfect for going 26.2 miles, or 13.1 in the accompanying Garry Bjorklund Half Marathon.

Records set in 2024: Women’s marathon course best, and men’s and women’s half marathon course bests. Oh, and Kenyan Elisha Barno claimed a race-record sixth men’s title.

“Distance running is a huge effort, and when the temperature gets even into the 50s, performance can suffer. There’s just not any way to dress well for the heat,” said Steve Harrington of Duluth, the race’s medical director for 25 years (1986-2010). “Our location on the shores of Lake Superior helps. The vast majority of the race days have been cool. Grandma’s Marathon got its reputation because of a fast course and good weather.”

The reputation remains, and Saturday’s races, which finish in Duluth’s Canal Park, are in demand. When registration opened last Oct. 1, the half marathon was filled in 18 hours with 9,762 runners and the marathon was filled in 37 days with 10,114 runners. All are event records.

Grandma’s is Minnesota’s oldest and largest marathon and ranked No. 10 in the United States in 2024 with 7,578 timed finishers.

We’ll see if weather luck holds Saturday as a heat wave flows through Minnesota; along the shore, the forecast is for damp weather with early morning temperatures in the 50s.

There was no magic to scheduling the first Grandma’s in 1977; the organizing North Shore Striders club had an open race date on the third Saturday in June. The inaugural run began at 11 a.m. and local Olympian Garry Bjorklund won by nearly five minutes in his first marathon in the heat.

Earlier start times followed, and Grandma’s cemented its stature in 1981 when Bjorklund pushed Dick Beardsley to victory in 2 hours, 9 minutes, 37 seconds. It tied the ninth-fastest men’s time in history. Lorraine Moller of New Zealand won in 2:29:36, the sixth-fastest time in women’s history.

Yes, the overcast, misty, 50-degree weather helped. And for years, Beardsley’s time stood as the fastest marathon ever run in June.

“Running along the lake means you need to be prepared for different micro-climates, all in one morning, as you get closer and then farther away from the water. That’s what [world masters star runner] Alex Ratelle told me, and that’s what I preach,” said former Grandma’s Marathon executive director Scott Keenan, who was in charge from the beginning and retired in 2013 after 37 years. “June in Duluth has been fabulous and [the race] has been lucky, and not just a little lucky.”

Other races haven’t been as fortunate. The 2023 Twin Cities Marathon, on Oct. 1, was canceled shortly before the scheduled start. The 2007 Chicago Marathon, on Oct. 7, shut down after 3 ½ hours, both because of heat.

American College of Sports Medicine guidelines assist race officials in safety decisions, says Harrington. Grandma’s has a three-person committee to address weather concerns, although a cancellation has yet to be discussed. Brief rain caused start delays in 1980 and 2002, and the 2016 race finished under an extreme caution warning because of heat.

Heat, however, is a rarity for the race, which travels from just south of Two Harbors to downtown Duluth. Lake Superior’s surface temperature is about 45 degrees during June, says meteorologist Joseph J. Moore of the National Weather Service in Duluth.

“For the most part, weather conditions in the early morning along Highway 61 [North Shore Drive] and [the concluding miles on] London Road are just about perfect,” Moore said. “It can be pretty darn chilly, and the [prevailing] wind is from the northeast, a tailwind.”

Grandma’s weather statistics gathered by Moore from the Iowa Environmental Mesonet confirm the race’s annual promotional pitch. Start-time temperatures are in the 40s, 50s and 60s. Discounting 1977, the morning low has reached 70 just once, in 2006. Not necessarily great for spectators, but good for athletes, who then make fewer visits to the finish line medical tent.

Two-time Olympian Volha Mazuronak of Belarus made the most of Duluth’s climate a year ago. At Grandma’s for the first time, at age 35 and the mother of a 15-year-old son, she ran a women’s course best of 2 hours, 23 minutes, 52 seconds to win by six minutes.

“To be honest, this was a surprise, because my preparation wasn’t good,” Mazuronak said at the time. “But as it turned out, this course is very good for fast results. The wind helped, and the weather was nice.”

There’s always a chance it will be cooler by the lake.

Now a masters-division runner, at age 40, Elisha Barno is back in the elite field with six men’s titles since 2015, including the last two.

Grandma’s course record holder Dominic Ondoro, 37, of Kenya is also entered and is the newest member of the Grandma’s Marathon Hall of Fame, along with former race board member Dave Malban of Duluth. Ondoro ran 2:09:06 in 2014.

The best previous time by a 2025 entrant is Kenya’s Pius Karanja, 33, with a 2:06:55 in 2022 at the Eindhoven Marathon in the Netherlands.

American Kellyn Taylor, 38, who set a then-women’s course best of 2:24:28 in 2018, is entered.

Five-time men’s champion Aaron Pike, 39, a Minnesota native, is in the wheelchair field.

Saturday’s races will use a separated start to provide a smooth flow for the record number of runners. The half marathon has start times of 5:50, 6, 6:10 and 6:20 a.m. The marathon has times of 7:35, 7:40, 7:45, 7:55 and 8:05 a.m.

While the 50th Grandma’s Marathon is still a year away, this week marks the 35th Garry Bjorklund Half Marathon. And the race namesake, from Proctor, Minn., now living in Fort Collins, Colo., will be in Duluth. Bjorklund is 74.

When: Saturday, 26.2 miles, starting from Two Harbors on North Shore Drive to Duluth’s Canal Park Drive. Wheelchair and adaptive, 7:35 a.m.; elite and semi-elite men, 7:40 a.m.; elite and semi-elite women, 7:45 a.m.; waves, 7:55 and 8:05 a.m.

Field: 10,114 registered runners compete for $107,450 in prize money ($10,000 each to men’s and women’s overall winners)

When: Saturday, 13.1 miles, starting from the Talmadge River on North Shore Drive to Duluth’s Canal Park Drive. Adaptive, 5:50 a.m.; elite and semi-elite, 6 a.m.; waves, 6:10 and 6:20 a.m.

Field: 9,762 registered runners compete for $26,425 in prize money ($3,000 each to men’s and women’s overall winners)