Should the Twin Cities Marathon have been cancelled?

Just hours before runners were expected to start the Medtronic Twin Cities Marathon, an alert went out from race organizers informing athletes that the marathon has been cancelled due to EAS black flag conditions predicted during the race.

Today’s marathon and 10 mile races are cancelled due to Black Flag EAS conditions. pic.twitter.com/6DpjE8CMi6

— Twin Cities In Motion (@tcmarathon) October 1, 2023

Based on weather forecasts from the National Weather Service and racecast.io, the day's highest predicted Wet Bulb Globe Temperature (WBGT) of 82º, while not reaching an official "Extreme" level, posed potential risks for the marathon, prompting organizers to consider other factors like water availability and medical aid, ultimately leading to the event's cancellation at a "Black" warning level. Race organizers are now working on credit options for participants.

What is the EAS Flag System?

The Event Alert System (EAS) is a color coded system that represents course conditions of the day. Ranging from low (green) to extreme (black) is typically indicative of a range of weather conditions but can also be used for other dangerous conditions on the course. Typically you’ll see a colored flag raised at each aid station on a marathon course that uses the EAS.

When it comes to temperature, especially heat, EAS is typically based on the Wet Bulb Globe Temperature (WBGT), or the temperature measured using a thermometer with its bulb moistened. The National Weather Service has forecasts for the WBGT which can be found here. We use a similar predictive equation for racecast.io and show a flag color based on those conditions.

Should the Twin Cities Marathon have been cancelled?

That depends. Based on forecasts from the National Weather Service and here on racecast.io, the highest the WBGT would reach today is 82º which, depending on the scale used, correlates to a red flag warning - not enough to justify canceling a race. However, the ranges for running events were originally developed for track and field by the USATF and World Athletics which are much shorter races than a marathon.

Without the WBGT being officially “Extreme” other factors come into play in determining the final EAS warning level including water on course and medical aid availability. Likely, with the heat forecasted near the end of the race warranting a level of “Extreme Caution” (red) combined with the confidence of race organizers to be able to handle those conditions, the overall event conditions were classified as “Black” which warrants cancelling the event.

What’s next?

Race organizers have issued a statement that they will figure out possible credit options and update athletes via email by end of day Thursday, October 5. There is no word yet on rescheduling any of the races aside from possibly running the elite race early Monday morning.