Rain and wind from Tropical Storm Beta lashed Caribbean islands off Nicaragua's coast Thursday, and the storm was forecast to strengthen to a hurricane and dump water onto already sodden hills inland.

Strong winds and light rain swept over the idyllic Corn Islands, many of whose lobster-fishing residents are of British West Indian descent.

"There's a lot of wind," said Naomi Gaitan, speaking by telephone from the island hotel where she works. "Since yesterday we've been without electricity."

Beta is the 23rd named tropical cyclone of an unrelenting Atlantic-Caribbean hurricane season, the most active since record-keeping began more than 150 years ago.

It was expected to reach Nicaragua's mainland with hurricane force late Saturday, and disaster services have begun preparing storm shelters in case evacuations are necessary.

Colombia issued a hurricane warning for its San Andres and Providencia islands near Nicaragua and began evacuating tourists and residents from San Andres.

Island residents were told to secure their buildings as the government brought in emergency supplies.

The storm could dump up to 20 inches of rain over parts of Nicaragua, Costa Rica, Honduras and Panama, already sodden after weeks of rain from Hurricanes Stan and Wilma.

"These rains could overflow rivers and provoke flooding and even mudslides," said Jose Ramon Salinas, head of the Honduran disaster agency.

Late Thursday, Beta had top sustained winds near 60 mph. It was about 35 miles southeast of San Andres.

The slow-moving storm was drifting to the north in the warm Caribbean, and hurricane conditions were expected over San Andres on Friday before the storm reaches Nicaragua's coast.

Weather forecasters switched to the Greek alphabet for storm names after using up their annual list of 21 names for the season with Wilma, which was at one point the most intense hurricane ever recorded in the Atlantic basin. It ravaged Mexico's Yucatan Peninsula and southern Florida and killed 28 people.