ORLANDO, Fla. — The first tropical threat of the hurricane season in Florida washed across the state overnight Friday, leaving South Florida residents and local officials to deal with flooding, power outages, stranded vehicles and hours of cleanup, affecting some businesses.

In Miami, drivers faced slashing rains and flooded streets in the early hours of Saturday morning. The city’s fire department responded to several people caught in cars amid the rising waters. Six high-water vehicles deployed in the city, the department said on Twitter. Winds of 40 miles per hour did not meet the threshold necessary for the system to be classified as Tropical Storm Alex, but they did slosh water into the downtown area, including in parking areas of condominiums.

The storm has brought more than 10 inches of rain to Miami over a 72-hour span, according to AccuWeather, but other areas saw higher totals, including Key Largo (which received 11 inches of rain) and Biscayne Park (11.6). There was also reported flooding in communities outside Miami including Hialeah and Hollywood, as well as in Naples, on the Gulf Coast.

Power outages did not soar overnight, however. As of 9 a.m. on Saturday, Miami-Dade County had 4,083 outages according to PowerOutage.us, though that number had dropped to 3,111 by early afternoon. The surrounding counties of Broward and Palm Beach reported 1,947 and 1,046, respectively.

To the west, Collier County, home of well-populated Naples, had 226 outages reported at 9 a.m., but only two by 11:30. Lee County, farther north along the Gulf Coast, had 47. By noon, all tropical warnings were canceled in most of southwest Florida as the storm pounded the Treasure Coast in the southeastern region, according to the National Weather Service.

Meteorologists said that although the storm never fully organized as it traveled from the Gulf of Mexico toward the Florida Keys, it could still strengthen into a tropical storm as it leaves the Atlantic coast. And Floridians know it does not take much storm development to cause mayhem in Miami — especially on a weekend night when many people are out.

Goncalo Gil, 26, stayed inside as streets clogged with water outside his apartment in the Miami neighborhood of Brickell. Mr. Gil, a student pilot, who posted a video of flooded streets on Twitter, wondered if the city’s flood prevention system, which included storm water pumps and sea walls, had worked as intended. “From midnight, everywhere was flooded, every car was stalled,” he said.

Kash Kashmiri, 30, arrived at the store he manages, Total Nutrition, in Brickell by 10 a.m. and found water inside its sandbagged entryway. He fretted over whether to allow a customer inside the store, and eventually offered to gather products for him and perform a cash transaction at the front door.

“Normal down here is where there’s a heavy storm, you can expect slight flooding,” he said by phone. “Any kind of tropical storm, you can expect flooding for sure.”

More than two hours into Mr. Kashmiri’s shift, the rain picked up again, and he noticed people in the area tying down furniture.

Warnings about continued possible weather risks remained for the weekend.

“The main threat right now is the potential for heavy rainfall and flash flooding,” said Maria Torres, a spokeswoman for the National Hurricane Center in Miami, on Friday.

Early Saturday, the center warned of “considerable flash and urban flooding” in South Florida. Rainfall totals were expected to be wide-ranging as the storm was forecast to travel toward Bermuda, possibly causing high currents along the Atlantic coast as it moved away from the mainland.

The forecast for Florida included the possibility of tornadoes over the southern portion of the state through Saturday. The Hurricane Center also said that some cities in the state could see a storm surge of up to three feet.

People who live in parts of South Florida that are prone to floods should identify a safe place to go to if waters begin to rise, and be careful not to drive through standing water, Ms. Torres said on Friday.

“Turn around, don’t drown,” she said.

Yet the region was dotted with drivers taking their chances during the early morning hours and into the afternoon, even as downpours drenched neighborhoods.

At an intersection in Miami’s Little Havana, dozens of cars paused at traffic lights to take measure of the flooded streets beyond. Most drivers of pickup trucks barreled through the rising water, sending white sprays in all directions.

Drivers of smaller cars could be heard through open windows discussing with their passengers the likelihood of getting through or getting stuck with a flooded engine — the fate of many vehicles elsewhere in the area. Tow trucks raced around, doing a brisk business.

“Which way should I go?” a man in a small S.U.V. asked a passerby. “I need to get to the liquor store.”

Whatever their priorities, plenty of drivers took to the streets as the storm began to abate during the afternoon, causing traffic jams worse than usual in the slick and inundated conditions.

“This is like the Rio Grande,” a woman said as she surveyed two flooded blocks.

But not everyone was awed by the effects of the storm. “This is nothing,” said Luis Garay, a 64-year-old handyman who has lived in Miami for 25 years and who recalled several hurricanes pounding his native Honduras when he still lived there. “We went through much worse than this.”

Mr. Garay blamed the flooded streets on drains blocked by trash. “People throw their garbage everywhere, and the city doesn’t always pick it up,” he said. “Now look at the mess.”

Nearby, a man on a bicycle sped up as he approached the flood. “¡Hay que mojarse!” he said. (“You have to get wet!”)

Concerns about dangerous weather in the Atlantic Ocean began this week, almost on cue with the arrival of hurricane season on June 1. Hurricane Agatha, the first named storm in the eastern Pacific region, roared into Mexico as a Category 2 storm with heavy rains and damaging winds. It killed at least nine people and left five others missing, the governor of the southern state of Oaxaca, Alejandro Murat, said on Friday morning.

Meteorologists expect an “above normal” Atlantic hurricane season, which runs through Nov. 30, with 14 to 21 named storms considered likely. Up to 10 of those are expected to reach hurricane strength.

Frances Robles, Alanis Thames and Jesus Jiménez contributed reporting.