The youngest victim was 12-year-old Uriel Escobar, who was electrocuted Friday after touching a downed power line, said Juan Carlos Orantes, the director of emergencies with the country's civil protection agency.
"He died in the hospital after being transported. He was accompanied by his grandfather when he died," Orantes said.
The death toll was expected to rise as investigators worked to confirm other incidents in the state of Oaxaca, Orantes said.
The victims ranged in age from 12 to 65 years old.
"We are expecting still more intense storms; however, we've had a brief stoppage for now," Orantes said.
In Veracruz, Alfredo Garcia, 21, was found dead in his car after it was overcome by floodwaters. In the same state, Damien Islas died while trying to save a group of people from a collapsing house, Orantes said.
The dead include five from Hidalgo, two from the state of Tamaulipas, another two in Guerrero, three more in Veracruz and three in San Luis Potosi.
Tropical Storm Arlene is the first named storm of the Atlantic hurricane season.