When the Giro di San Francisco comes to our front yard, it must be Labor Day! pic.twitter.com/UL0Fe1oL73— Jonathan Bloom (@BloomTV) September 4, 2017
Hundreds of cyclists of all ages are taking part in the event, which includes 10 races.
The first race begins at 8 a.m., and the final pro race will start at 3 p.m.
The races will prompt streets closures near Levi's Plaza, the Embarcadero, Battery and Front streets.
Click here for more information about the races.
Click here for live traffic maps.