On Saturday, Ileana moved northward over the southern Gulf of California at 9mph, according to the US National Hurricane Centre.
It was about 75 miles north-northeast of Cabo San Lucas with maximum sustained winds of 40mph, the centre said.
A tropical storm warning was in effect for portions of the Baja California peninsula, including Cabo San Lucas and San Jose del Cabo.
Forecasters predicted four to six inches of rain would fall with Ileana, and up to 12 inches was possible for coastal areas of Michoacan, Colima and Jalisco states on Friday.
Tropical storm conditions are expected to begin in portions of Baja California Sur during the next several hours where tropical storm warnings are in effect.
This heavy rainfall will bring a risk of flash flooding and mudslides to portions of western Mexico and southern Baja California.
Juan Manuel Arce Ortega, from Los Cabos Civil Protection, said: “The entire municipalities of La Paz and Los Cabos are already on red alert.
“This means that efforts are already under way to inform the population, as well as the implementation (of measures) and evacuation to temporary shelters.”
He also urged residents to avoid crossing rivers, streams and low areas where they can be swept away by water.
Oscar Cruces Rodriguez, of Mexico’s federal Civil Protection, said in a statement that residents should avoid leaving their homes until the storm passes and if they are in an area at risk of flooding to find temporary shelters.
Authorities prepared 20 temporary shelters in San Jose del Cabo and Cabo San Lucas, according to Los Cabos Civil Protection.
Rain remained consistent through Los Cabos on Friday afternoon, with several roads flooded and some resorts stacking up sandbags on their perimeters.
Some people were still walking around boat docks with their umbrellas.
“The priority has to be safety, starting with the workers. We always have to check on our colleagues who live in risk areas,” said Lyzzette Liceaga, a tour operator at Los Cabos.