PHILADELPHIA (CBS) — Philadelphia Marathon weekend is here. Some 21,000 runners will snake their way through the city, but it may lead to some challenges if you live along the route.

All three races will kick off at North 22nd Street and the Benjamin Franklin Parkway. Winds are expected to die down and the temperatures will be moderate — which is perfect weather for running.

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“The city looks amazing. The runners, they’re ready to run,” race director Kathleen Titus said.

And we’re off, to another marathon weekend. Saturday is the half marathon and 8K, and Sunday is the full marathon. It’s the 27th year for the race and it’s the city’s only full-length marathon.

“From a heartfelt thank you from the city of Philadelphia, thank you to each and every one for making this weekend a success,” City Representative Sheila Hess said.

Marathon weekend kicked off Friday afternoon with the expo at the Convention Center. Runners come from all 50 states, 38 countries and range in age from 11 to 90 years old.

“There’s an energy and excitement that just makes it worth doing,” legacy marathoner Mark Sullivan said.

Sullivan has run in every Philadelphia marathon dating back to 1994. The race was held virtually last year due to the pandemic.

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“Philly is a big sports town and when you run in the marathon on Sunday, you’re the home sports team,” Sullivan said.

But the cheers may turn to jeers.

The center lanes of the Parkway were shut down by Friday afternoon and by Saturday morning, there will be dozens of other road closures and parking will be prohibited along the routes.

Cars parked around Pennsylvania Avenue, the Art Museum and Parkway will have to move by 2 a.m. Saturday and will be displaced through 5 p.m. Sunday. SEPTA bus routes are also being detoured.

Despite the inconvenience, race organizers say they’re ready for a successful weekend.

“It’s absolutely amazing. The vibe is exhilarating,” Titus said.

Unlike the Broad Street Run from a few weeks ago, they are encouraging people to come out to cheer on the runners.

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For a complete guide of race day closures and info, click here.