MIAMI — Tropical storm Barry weakened into a tropical depression as it moved through Tampa Bay on Saturday, though its rains brought some relief to the drought-parched region.

Forecasters discontinued the tropical storm warnings and watches issued for stretches of the Gulf Coast. The depression's sustained winds had slowed to near 56 km/h and it was moving north-northeast at about 37 km/h.

The storm made landfall in the Tampa Bay area around 10 a.m. EDT, according to Daniel Brown, a meteorologist at the National Hurricane Center.

"The landfall in a case like this is kind of insignificant," Brown said.

In Mexico, tropical storm Barbara made landfall Saturday on the southern Pacific coast near the Guatemala border, an area notoriously vulnerable to flooding.

With maximum winds of nearly 80 km/h and higher gusts, Barbara was centred just southwest of the Mexican city of Tapachula. The storm was heading northeast at 11 km/h, and was expected to weaken as it continues moving inland over southeast Mexico and western Guatemala, the hurricane centre said.

A tropical storm warning was in effect from Sipacate, Guatemala, to Barra de Tonala, Mexico, and the hurricane centre warned that Barbara could unleash life-threatening flooding and mudslides. Heavy rains were reported.

Rain was falling throughout drought-stricken Florida and Georgia, where the dry conditions have fed wildfires for weeks.

"We're hoping several of these fires will not be a problem anymore," said the Florida Division of Forestry's Mike Newell. "It's too early to tell right now. Everybody's basically waiting for the rain to stop to go out and see what's going on."

The depression was expected to drop seven to 15 centimetres of rain on parts of those states, along with South Carolina and North Carolina on Saturday. Isolated areas could get up to 25 centimetres of rain.

The National Weather Service said isolated tornadoes over central Florida were possible.

A tropical storm warning was cancelled after being issued from Bonita Beach on Florida's southwest coast northward to Keaton Beach, near the state's Big Bend area. A tropical storm watch for the area between Keaton Beach west to St. Marks, south of Tallahassee, also was cancelled.

The storm developed Friday, the first official day of a hurricane season that forecasters have said they expect to be busier than normal. The National Weather Service said it expects 13 to 17 tropical storms, with seven to 10 becoming hurricanes and three to five in the strong category.

"There is no correlation at all between activity in the early part of the season and later parts," said Lixion Avila, a hurricane specialist at the centre.

Barry formed more than three weeks after the first named storm of the year - subtropical storm Andrea - developed off Florida's eastern coast. Andrea skirted the southern Atlantic coast but caused minimal damage.