Tropical Storm Danielle formed off eastern Mexico on Monday and began drenching the country's Gulf coast region with heavy rains.
The U.S. National Hurricane Center in Miami said Danielle's maximum sustained winds increased to near 45 mph, with some slight strengthening expected before the storm was forecast to make landfall later in the day.
A tropical storm warning was in effect for a stretch of the Gulf coast state of Veracruz, from Laguna Verde to Rio Panuco.
The storm was centered about 55 miles east of the port of Tuxpan and was moving west at 7 mph.
Danielle was expected to produce 6 to 10 inches of rainfall over several Mexican states, with isolated amounts up to 15 inches in higher terrain.
The Veracruz government cancelled classes in most of the state as a precautionary measure. Schools are sometimes used to shelter storm victims in Mexico.
There were no immediate reports of any damage or significant flooding, but the Hurricane Center warned that flash floods and landslides were possible.
Danielle was expected to make landfall along a sparsely populated stretch of coast south of Tuxpan.