Hurricane Jova slammed into Mexico's Pacific coast as a Category 2 storm early on Wednesday, killing three people and injuring six.
Meanwhile, a tropical depression hit farther south and unleashed steady rains that contributed to 13 deaths across the border in Guatemala.
Jova came ashore west of the Mexican port of Manzanillo and the beach town of Barra de Navidad before dawn with 100 mph winds and heavy rains, before moving inland and weakening to a tropical depression by afternoon. It continued to dump rain over a large swath of northwest Mexico, including Jalisco state where rainfall this year had been low.
A 71-year-old woman drowned in Colima state after a strong current swept away the car in which she and her son were riding. Her son survived, Colima Governor Mario Anguiano said.
In the neighbouring state of Jalisco, Jova triggered a mudslide in the town of Cihuatlan, just inland from Barra de Navidad, that swept away a house on a hillside, killing two of its occupants, said Oscar Mejia, the spokesman for the Jalisco state Red Cross rescue division.
Farther northwest along the Mexican coast, in the town of Tomatlan, two children suffered head injuries when the walls of their brick home collapsed under the force of the wind and rains, Mejia said.
The new tropical depression formed in the Pacific off far-southern Mexico near the Guatemala border, with maximum sustained winds near 35 mph, the US National Hurricane Centre reported. The storm quickly moved ashore over Mexico and was expected to move slightly north before dissipating before day's end.
The storm was smaller and less powerful than Jova, but the mountainous terrain of southern Mexico state of Chiapas and neighbouring Guatemala is particularly vulnerable to flash flooding and mudslides. Numerous Indian villages perch precariously on hillsides.
Guatemalan President Alvaro Colom blamed rain from the storm for the deaths of 13 people in his country. At least four of those were electrocuted when contacted power lines, Mr Colom said. Others died in mudslides or were swept away by swollen rivers.
National Hurricane Centre forecaster John Cangialosi said the rains in Guatemala probably were linked to the tropical depression, even though it had not yet hit land. "If they're in Guatemala, they're pretty close to the circulation center of the system, and it has been a very slow-moving system ... so it's likely linked to this feature," Cangialosi said.