Rally-goers huddled under umbrellas and plastic tarps, or stood dripping as Clinton spoke.
“You must get out! Let's vote for the future. Let's vote for what we want for our country!” she said to close a boiled-down, seven-minute version of her usual stump speech.
She also made stops at an early voting center in Miami and a campaign field office in Miami's Little Haiti.
Clinton will campaign later Saturday in Philadelphia, and in New Hampshire on Sunday. It is not clear whether she will return to Florida before Election Day. Clinton will be joined in Philadelphia by pop singer Katy Perry and in Manchester by singer James Taylor.
Former president Bill Clinton was also in Florida on Saturday, campaigning on his wife's behalf.
Clinton holds a 1.2 percentage-point lead in Florida in the RealClearPolitics average of recent polls — far closer than many Democrats had predicted with just three days to go. Her lead was four points in the same average on Oct. 22, but the race had already begun to tighten before the surprise announcement on Oct. 28 that the FBI would revisit its investigation of her State Department email.
Clinton could still win without Florida's 29 electoral votes, but a victory here is her safest and fastest way to the 270 electoral college votes needed.
Trump claims momentum in Florida, where he is a part-time resident, but Democrats say they are encouraged by the large turnout for early voting in key Democratic counties and among Latinos.
Clinton was introduced here by Sybrina Fulton, whose son Trayvon Martin was shot and killed by a neighbor in 2012 in a racially charged case that helped propel a movement for criminal justice reform. Fulton has campaigned alongside Clinton frequently this year, but her presence in South Florida was part of an effort to rally liberal voters in a crucial state. Clinton visited Sanford, Fla., where Martin was killed, last week.
Rep. Patrick Murphy (D-Fla.), who is running behind in his challenge to supplant Sen. Marco Rubio (R-Fla.), was among the speakers before Clinton took the stage.