A day later, on August 6, Ileana began to develop an eyewall structure as it reached its peak intensity with winds of 65 mph (100 km/h) and a pressure of 998 mbar (29.47 inHg).

Once the wave entered the Eastern Pacific Ocean early on August 4, thunderstorm and convective activity rapidly increased.

[2] After satellite imagery indicated that an area of low pressure had formed a few hundred miles south of the Gulf of Tehuantepec and was showing signs of organization, the NHC raised the system's two-day development chances to 50% around 17:00 UTC on August 4.

[3] Only an hour later, at 18:00 UTC, the system was designated as a tropical depression while located about 230 mi (370 km) south-southeast of Puerto Angel, Mexico.

[4] Six hours later, the structure of the depression had degraded due to northerly wind shear caused by the stronger disturbance that would later become Hurricane John.

[8] Ileana reached peak intensity on August 6 at 12:00 UTC with maximum sustained winds of 65 mph (100 km/h) and a minimum central pressure of 998 mbar (29.47 inHg), while located approximately 115 mi (185 km) southwest of Acapulco.

[10] By 21:00 UTC on August 6, Ileana had become increasingly intertwined in the outer bands of Hurricane John to the west as the two systems began to experience the Fujiwhara effect.

[1] As a precautionary measure, the Government of Mexico issued a tropical storm watch for the country's Pacific coast from Lázaro Cárdenas, Michoacán, to Cabo Corrientes, Jalisco, on August 5 at 22:40 UTC.

[19] In the municipality of Santiago Choapam in Oaxaca, heavy rains from Ileana caused a landslide that left a house in ruins.

A vehicle containing 18 individuals was swept away by water currents while attempting to cross a flooded bridge; three children and one adult were later found dead.

The Mexico City Metro (STC) also implemented safety measures for several of its lines,[23][24] such as the manual operation of trains and decrease in travel speed.