Chicago Weather

2021 Chicago Marathon Weather: Race Day Temps Could be Warmest in 10 Years

NBCUniversal Media, LLC

There's some good news and some not-so-good news in the forecast for this year's Bank of America Chicago Marathon.

While there were questions earlier in the week on whether the race would stay dry, models Friday showed mostly dry conditions for runners. Though there remains a chance for a shower in the afternoon, most areas look to stay dry for the day.

The tricky part will likely be the temperatures, which could reach levels not seen in the last 10 years.

Temperatures for the start of the race Sunday look to be near 70 degrees. The last time it was this warm to start the race was in 2007, according to the NBC 5 Storm Team.

The day is expected to stay warm and humid, with temperatures peaking in the afternoon as they reach into the mid 80s.

In advance of the race, marathon organizers are communicating with runners through an event alert system to help them prepare for warmer conditions.

"We are likely to be starting in a yellow, which is less than ideal," said Dr. George Chiampas, medical director for the Chicago Marathon. "We may need to go to a red based on the temperatures."

Chiampas said runners can do a few things ahead of times to help.

"Salt supplements and electrolyte supplements [are] really what we want to be concentrating on Sunday," he said, "because your fluid losses are going to be at a larger level with ... a little bit of an increased humidity." 

Marathon organizers say runners should plan on dressing in light, loose clothing for the race. In addition, now might be the time to reframe expectations.

"If they need to walk more, if they need to reset their goals, Sunday may not be the day when they're setting their PR or their personal best," Chiampas said.

Check back throughout the weekend as the NBC 5 Storm Team will continue to update developing forecasts.

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