Three shelters throughout the county were open and had attracted 154 residents, most of them at Booker T. Washington and Robert Morgan high schools in south and central Miami-Dade. Also, the county had helped transport 292 residents to special needs centers around the county.

Miami leaders said they, too, are prepared for the worst.

“We believe we are going to experience lots of local flooding and strong winds,’’ Miami Mayor Tomas Regalado said.

Regalado said city crews have set up pumps in flood-prone areas, such as Brickell. Portable pumps also are being readied.

“We have been preparing for this for months,’’ Regalado said.

Homestead officials appeared to breathe a sigh of relief that Isaac had not caused greater harm, particularly to the city’s significant agricultural industry.

“It looks like we’re dodging a bullet,’’ County Agricultural Manager Charles LaPradd said.

Winter is the busiest season for Homestead’s farmers, but there are still avocados in the groves. Heavy rains can kill avocado trees, and gusty winds can knock the fruit to the ground.

But the storm appeared to cause more damage to small business owners than to farmers.

At about noon, power went out along on Washington Avenue in downtown Homestead, where small shops cater to Mexican, Guatemalan and Central American customers.

About 400 homes and businesses were affected by the outage, among them La Michoacana ice cream shop.

Miguel Chavez, manager of the shop, said he expected losses in the thousands of dollars. The shop has a 10-by-8 foot freezer, as well as display cases, filled with ice cream, including flavors not typically found in stores, such as chili pepper.

“Today is a day the hurricane threatens our business,’’ Chavez said after the power outage. “You can’t fight against nature.’’

EMERGENCY DECLARED

Florida Gov. Rick Scott has issued a state of emergency, expressing concern about the damage Isaac might do once it passes the Keys and fuels up in the warm Gulf of Mexico. It was forecast to grow into a Category 2 Hurricane with 100 mph winds as it approaches the Panhandle.

“The issue in the Panhandle is flooding,’’ said Scott, who noted that the region is still saturated from Tropical Storm Debby, which the region with rain in June.

Scott said he cleared his calendar through Tuesday, and will be in Tampa only on Sunday.

“We may need to help out other states,’’ he said.

Scott said he spoke with Republican presidential candidate Mitt Romney twice on Saturday. They talked about safety, emergency management measures and the situation in Tampa, he said.

Rick Knabb, director of the National Hurricane Center in West Miami-Dade, said that a strengthening Isaac in the Gulf could pose a storm surge threat to Tampa Bay, where the Republican National Convention was scheduled to convene Monday in an area vulnerable to flooding. Events will now be delayed until Tuesday afternoon.

In Miami-Dade, officials also issued an evacuation order for people living in mobile homes, unsafe buildings and homes in low-lying, flood-prone areas. The Keys did the same, adding an order for boat dwellers to seek safer shelter.

Miami Herald staff writers Dan Chang, Alexandra Leon, Hannah Sampson, Carli Teproff, Charles Rabin, Julie K. Brown, Christina Veiga, Cammy Clark, Kathleen McGrory and Jacqueline Charles in Haiti contributed to this report.