MEXICO CITY (AP) — Tropical Storm Delta rapidly strengthened into a hurricane in the Caribbean Monday, aiming to hit Mexico's Yucatan Peninsula potentially as a major storm before continuing on to strike the U.S. Gulf coast later in the week.

That part of Mexico is still soaked from Tropical Storm Gamma which hit its popular coastal resorts over the weekend and forced thousands from their homes in Tabasco and Chiapas. Gamma weakened to a tropical depression Monday after leaving six dead in southeastern Mexico. It continued to break up just north of the Yucatan Peninsula.

Delta had been forecast to strike western Cuba, but shifted a bit to the west Monday putting it on a path to scrape the northeast tip of the Yucatan early Wednesday. It was moving into an area with very warm water and nearly calm high winds that forecasters at the hurricane center called “a very conducive environment for strengthening."

The U.S. National Hurricane Center said Monday evening that a hurricane warning was in effect for the Cuban province of Pinar del Rio and in Mexico, from Tulum to Rio Lagartos, as well as Cozumel.

Delta is then forecast to make landfall on the U.S. Gulf Coast around Friday. While there is a large uncertainty in track and strengthening five days out, “there is a risk of dangerous storm surge, wind, and rainfall hazards along the coast from Louisiana to the western Florida Panhandle," the hurricane center said.

Mexico's civil defense agency said in a statement that four of the deaths blamed on Gamma, including two children, were in Chiapas, where a landslide on a mountainous slope buried their home. The other two deaths were in Tabasco state, where one person was dragged away by the water and another drowned.

Gamma, along with cold fronts, combined over the weekend to cause extreme rains in parts of the Yucatan Peninsula and Chiapas, affecting more than half a million people. The hardest-hit state was Tabasco, where more than 3,400 were evacuated to shelters.

The hurricane center said Monday that Gamma was about 115 miles (190 kms) east-northeast of Progreso, Mexico, and had maximum sustained winds of 35 mph (55 kph). It was moving southwest at 5 mph (7 kph). Forecasters predicted up to 8 more inches of rain in the states of Yucatan, Campeche and Tabasco, producing significant flash flooding.

Delta is the earliest 25th named storm to form in the Atlantic, beating the old record of Nov. 15, 2005, according to Colorado State University hurricane researcher Phil Klotzbach.

Delta had top winds of 75 mph (120 kph) Monday evening and was about 220 miles (355 kilometers) south-southeast of Grand Cayman. It was moving west near 8 mph (13 kph), on track to pass southwest of the Cayman Islands early Tuesday.

A tropical storm warning was issued for the Cayman Islands and a hurricane watch was in effect for western Cuba and its Isle of Youth. Forecasters warned of heavy rainfall, flash flooding and mudslides in parts of Jamaica, the Cayman Islands and western Cuba.

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AP writer Seth Borenstein in Washington contributed to this report.