Good weather outlook for Grandma’s Marathon weekend in Lake County

Clearing skies changed the weekend equation for Grandma’s Marathon fast. After a damp start to race week, the forecast called for the wet weather to move out by Friday night, leaving runners, volunteers and spectators with drier, sunnier and less windy conditions for Saturday morning along the North Shore.

Friday’s William A. Irvin 5K still carried a small weather risk, with isolated afternoon showers possible and temperatures in the low to mid-60s. That made the shorter race a more flexible outing than the main road races, but it also meant anyone planning to line the route or work the event needed to be ready for a few passing clouds and a wet patch before the evening turned calmer.

The more important shift came for Saturday’s Garry Bjorklund Half Marathon and Grandma’s Marathon. At the 6 a.m. start in Two Harbors, the forecast showed partly cloudy skies, light northwest winds and a temperature near 51 degrees, close to ideal conditions for a long road race. As runners moved down Highway 61, the air was expected to warm gradually, to about 55 degrees near French River late in the morning, around 64 degrees in Canal Park by midday and roughly 66 degrees later in the afternoon. Winds were expected to stay light, in the 2 to 8 mph range, with little sign of the kind of tailwind that can sometimes help a fast field.

That pattern mattered for more than finish times. For runners, it meant cool early miles and manageable conditions through the long descent toward Duluth. For spectators and volunteers, it pointed to a more comfortable day on the shoulder of Highway 61, at aid stations and around the finishing stretch in Canal Park, though the biggest congestion was still expected at both the start and finish lines. Minnesota Department of Transportation also warned motorists to expect increased traffic and delays on Saturday, with detours on I-35 and Highway 61 in Duluth to handle marathon traffic.

The weather forecast landed against the backdrop of a race weekend that has grown from 150 participants in 1977 to more than 20,000 each June. Grandma’s Marathon said more than 235,000 runners had already finished in Canal Park, with the quarter-millionth finisher expected during the 50th annual running in 2026. The event, sold out this year, generated almost $40 million in annual regional economic impact and depended on close to 3,500 volunteers, more than 85 sponsors, the Young Athletes Foundation and the Charity Partners Program to keep the weekend running.