A storm named Boris that is lingering off Mexico's west coast was downgraded to a tropical depression on Wednesday, but is still packing heavy rains that could cause deadly flash floods and mudslides.

The warning from the US National Hurricane Center said Boris could dump as much as 20 inches (50 cm) of rain in some parts of the states of Chiapas and Oaxaca.

Boris was expected to make landfall later Wednesday, according to the center's tracking map.

The storm was packing maximum sustained winds of almost 55 kilometres (35 miles) per hour, down slightly from Tuesday. It was still moving toward the north at seven kilometres (five miles) per hour.

As of 0900 GMT, the storm was 140 kilometres (85 miles) from the town of Salina Cruz, the center said.

But Boris is expected to weaken later Wednesday.

Tropical storm Boris to slam Mexico, Guatemala
Tuxtla Gutierrez, Mexico (AFP) June 03, 2014 - Tropical storm Boris bore down on Mexico's Pacific coast Tuesday, bringing drenching rains all the way to the Guatemala border, days after deadly flooding and mudslides in the region.

The storm is expected to make landfall as a tropical depression on Wednesday between the southwestern Mexican states of Oaxaca and Chiapas, according to a US National Hurricane Center tracking map.

The Miami-based center said the storm would likely produce life-threatening flash floods and mudslides.

The storm was packing maximum sustained winds of almost 65 kilometers (40 miles) per hour. It was moving toward the north at seven kilometers (five miles) per hour.

Mexico's National Weather Service said the storm was 125 kilometers (77 miles) from the Chiapas town of Boca de Pijijiapan at 1800 GMT.

Boris was expected to dump as much as 10 to 20 inches (25 to 50 centimeters) of rain over a large part of southern Mexico through Saturday.

As many as 30 inches (75 centimeters) are likely in mountainous regions of Oaxaca and Chiapas, the NHC said, while Guatemala was expected to see five to 10 inches (12.5 to 25 centimeters).

In Guatemala, rough weather produced a landslide that killed five people near the Mexican border on Saturday.

The national disaster relief agency said as many as 100,000 people have been affected by the inclement weather that has caused damage to homes and roads. Schools have been closed in parts of Guatemala.

Last week, the remnants of Hurricane Amanda were blamed for three deaths in Guerrero and the neighboring state of Michoacan.