Updated 2026 Grandma's Marathon Weekend Weather Forecast

Grandma's Marathon Weekend is arriving in the Twin Ports area, with thousands of runners and spectators arriving in Duluth and the surrounding area for the three major race events of the weekend.

As I'm sure you are well aware, this is an especially big year, as Grandma's Marathon celebrates its 50th anniversary. This huge milestone in the event's history helped propel this year's races to record sellouts.

With all of the runners and spectators ready for Friday's William A. Irvin 5K, Saturday morning's Garry Bjorklund Half Marathon, and Grandma's Marathon, plus the live music at Bayfront Festival Park and all of the other festivities, how will the weather be for these events?

Here's an event-by-event breakdown of the weather forecast that we'll keep updated as any details in the forecast change.

Friday Afternoon - William A Irvin 5K, Kids Events

Rain showers and thunderstorms are possible through 8 pm, with temperatures in the mid-60s. A southwest breeze of 5-10 mph is expected through the afternoon in Canal Park for the 5K and after.

Friday Evening - Entertainment Concert (Duluth)

Rain chances diminish into the evening hours, with temperatures dipping from around 60 at 7 pm to around 55 degrees by 11 pm. Winds will shift to out of the west at 5-10 mph.

Saturday Morning - Grandma's Marathon Starting Line (Two Harbors)

Temperatures at the starting line near Two Harbors will start near 50 degrees at 6 am, reaching 55 degrees by 8 am. Partly cloudy conditions are expected with a northwest breeze of 5-10 mph as races get underway.

Saturday Morning - Gary Bjorklund Half Marathon/Grandma's Marathon Finish Line (Duluth)

Temperatures will start at around 50 degrees at 6 am at the starting line in Canal Park, reaching 60 degrees by 10 am, and near 70 degrees by early afternoon. Partly cloudy conditions are expected, decreasing as the day goes on. A northwest breeze of 10-15 is expected through the morning.

Saturday Daytime (Duluth)

Temperatures in Canal Park will get up to around 70 degrees by mid-afternoon, with partly cloudy conditions. The wind remains out of the northwest through the afternoon, calming down from 10-15 mph to 5-10 mph by evening.

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Saturday Evening - Entertainment Concerts (Duluth)

Temperatures in Canal Park will dip from near 70 degrees at 6 pm down to around 60 degrees by 10 pm, bottoming out in the mid-50s overnight. Sky conditions are expected to remain partly cloudy with the breeze out of the northwest continuing to diminish down to 3-5 mph in the evening.

2025 Grandma's Marathon & Garry Bjorklund Half Marathon Photos

After strong thunderstorms overnight, this year's races started a half hour later than originally scheduled. While some clouds and fog kept things relatively cool early in the races, humidity and warmer temperatures quickly took hold with the full marathon underway.

Despite that, history was made with the first American winning Grandma's Marathon since 2009. He is also the first person to have ever won both Garry Bjorklnd Half Marathon (which he did in 2023) and Grandma's Marathon this year.

Gallery Credit: Nick Cooper - TSM Duluth