The annual Scotiabank Calgary Marathon is back this weekend, and with it, lots of excitement and a few key road closures.

Closures start at 6 a.m. MT on Sunday to accommodate races starting an hour later. Roads will be closed up to 3 p.m.

The big one to remember is Memorial Drive, which will be closed between 10th Street N.W. and Crowchild Trail. For a full list, scroll to the bottom of this article or check out the interactive map on the marathon's website.

Motorists are encouraged to avoid the downtown core, especially the Beltline, on Sunday. Expect to see lots of runners in Mount Royal, Bankview and Garrison Woods, as well.

Organizers are expecting roughly 20,000 volunteers, spectators and runners.

"We definitely prepare for all sorts of weather. It's May, it's Calgary. It could be anything, as we all know. We did meet with our medical team on Monday," race executive director Kirsten Fleming told the Calgary Eyeopener. "We have lots of people that are watching that very closely."

Environment Canada is predicting sunshine with a high of 25 C.

This map shows the roads affected by the various Calgary Marathon routes on Sunday. Check the marathon's website for specific route details. (Scotiabank Calgary Marathon/Google Maps)

Registration is down slightly in the longer races, such as the half marathon, full and ultra. Fleming said she expects that's due to the excessive snow and ice over this winter that made it unsafe for many people to train.

"You had to be pretty hardcore to train for a 50-kilometre over this winter here in Calgary, but certainly the five-kilometre, 10-kilometre numbers are doing great," Fleming said.

You can still register to run or volunteer, too. They're looking for course marshals in particular.

If you want to watch, the beer garden opens at 10 a.m. and there will be food trucks.

'Going for gold'

Also, several elite athletes will be returning for the national championship races — with $55,000 in total prize money up for grabs in the high-performance program.

Local runner Trevor Hofbower, who came third in 2015, will be back for the half marathon.

"He's not going to be happy with anything," Fleming said. "He's very humble but he's going for gold."

He'll be up against two Kenya-born race stars, Benard Onsare of Calgary and Kip Kangogo of Lethbridge, Alta.

Kip Kangogo broke the men's marathon record at the 2014 Calgary Marathon Sunday. (Scotiabank/MARKETWIRE)

Among the women to watch will be a trio, Rachel Hannah (Ontario), Sasha Gollish and Dayna Pidhoresky.

"They're fierce competitors and great friends, so it's always fun to see them," she said.

There's always a few quirky racers, too, to keep things light. Last year's event was marked by a Guinness World Record attempt, with 112 people running it while tethered together.

A group of 113 racers linked together with surgical tubing finished the Calgary Marathon, hoping to break a world record and raise awareness for mitochondrial disease. (CBC)

At the end of the race, for the first the marathon will offer four kiddie pools filled with ice and little cold towels for runners to cool off, an idea inspired by the marathon in Chicago. Along the race track, runners can grab cool sponges and lots of water.

Road closures are from 6 a.m. to 3 p.m. on Sunday:

North:

Memorial Drive will be closed from 10th Street N.W. to Crowchild Trail. It will be down to one lane in each direction from 10th Street N.W. to the Reconciliation Bridge at 4th Street N.E.

4th Street N.E. will be down to one lane on the eastern side between First Avenue N.E. to Riverfront Avenue.

First Avenue N.E. will be closed between 12th Street N.E. and Fourth Street N.E.

12th Street N.E. will be closed south of First Avenue, including Memorial Drive overpass.

Zoo Road N.E. will be closed, including Baines Bridge and Memorial Drive on/off ramp.

South:

Riverfront Avenue will be closed between First Street S.W. and Sixth Street S.E.

Fourth Street S.E., known as Olympic Way, will be closed from Ninth Avenue S.E. to Stampede Trail.

Ninth Avenue S.E. will be closed from Third Street S.E. to 12th Street S.E.

12th Street S.E. will be closed north of Ninth Avenue, including bridge to zoo.

11th Avenue will be down to two westbound lanes from Olympic Way to 14th Street S.W.

Fifth Street S.W. will allow northbound traffic only from 18th Avenue S.W. to Elbow Drive.

Southbound Elbow Drive will be down to one lane on the right side from Fifth Street S.W. to 30th Avenue S.W.

On Crowchild Trail S.W., the Flanders Avenue ramps will be closed in both directions.

Eastbound 50th Avenue S.W., also partially known as Mount Royal Gate S.W., will close its right lane between Crowchild Trail and 21st Street S.W.

For more information on the race's impact on motorists, check the City of Calgary's special events road closure website.

Hear more about plans for the Calgary Marathon:

With files from Angela Knight and the Calgary Eyeopener.