Today’s the day that more than 20,000 runners will make their way from downtown Minneapolis to downtown St. Paul during the Twin Cities Marathon and 10-Mile, causing detours and road closures. Add about 5,000 volunteers and thousands of spectators and you have yourself a massive traffic challenge around key parts of the Twin Cities.

Marathon officials suggest using Interstate 94 and I-35W in Minneapolis to bypass the racecourse. In St. Paul, motorists are advised to use I-35E, Ayd Mill Road or Grand Avenue to get around the finish line near the State Capitol.

Traffic will be able to cross the course at a few intersections — such as Lake Street near Lake Calhoun — at the discretion of course marshals.

The 10-mile run begins at 7 a.m., and the marathon follows at 8.

In St. Paul, 12th Street from Wabasha to John Ireland Boulevard will be closed from 5 a.m. to 6 p.m. Sunday. Summit Avenue between Ramsey Street and Portland Avenue will be closed all morning until 6 p.m. Sunday.

In Minneapolis, downtown streets between 5th and 11th avenues and 6th to 3rd streets will be closed from 5 a.m. to 9 a.m. Other road closings along the route Sunday include:

Miles 0-1 — 7 to 8:45 a.m.

3-8 — 7:30 to 10:20 a.m.

8-12 — 7:30 to 11:15 a.m.

12-15 — 7:30 to noon

15-21 — 7 a.m. to noon

21-26 — 7 a.m. to 2:30 p.m.

Visit startribune.com for our unofficial guide to the race.

staff report