Tropical Storm Arlene strengthened slightly as it neared landfall Thursday morning along Mexico's eastern coast, the National Hurricane Center reported.
Arlene, the first named storm of the 2011 Atlantic hurricane season, was moving west at about 9 mph, with sustained winds of 65 mph.
Authorities in the Mexican states of Tamaulipas, Veracruz, San Luis Potosi and Nuevo Leon braced for heavy rains. Forecasters from the National Hurricane Center warned of possible flash floods and mudslides.
With Arlene's early appearance, the 2011 hurricane season's start is remarkably similar to 2010, when Tropical Storm Alex formed in late June and went on to hit northeast Mexico as a Category 1 hurricane.
Meanwhile, tropical moisture associated with Arlene is streaming toward Florida, producing cloudy skies, rain showers and storms.
CNN contributed to this report