The tropical depression in the southern Gulf of Mexico strengthened into a tropical storm Tuesday afternoon, according to the National Hurricane Center.
Tropical Storm Cristobal was named just before noon when it developed maximum sustained winds of up to 40 mph.
Cristobal is the first named storm to develop in the Gulf of Mexico this year. Hurricane season began Monday.
The storm was moving slowly southwest Tuesday afternoon and is expected to meander over the southern Bay of Campeche through late Wednesday, according to the National Hurricane Center.
The storm could produce between 10 inches and 20 inches of rain in parts of Mexico and Honduras in coming days, the center said. The depression already has caused deadly flooding in parts of Guatemala and El Salvador.
The storm is forecast to begin moving northward across the Gulf of Mexico, according to the center.
It still was too early on Tuesday to say where the storm might make landfall, forecasters said.