A westward moving tropical depression gradually developed on August 17 south of the Mexican coast, attaining hurricane status two days later.

Executing a small counter-clockwise loop, Hilary degraded to tropical storm intensity and took a northerly track for the remainder of its existence.

Banding features slowly increased in coverage, and on August 18, the depression intensified, becoming Tropical Storm Hilary about 100 mi (160 km) south of the Pacific coast of Mexico.

[3] Moving northwest on a track parallel to the coast of Mexico at around 10 mi (16 km) due to a complex steering pattern,[1] Hilary was initially poorly organized and its low-level circulation was tough to find.

[1] Even though most computer models expected Hilary to remain offshore, meteorologists suggested there was a possibility of making landfall near Manzanillo.

[1] Under weak steering currents, Hilary became a major hurricane, a cyclone with winds of 111 mph (190 km/h) or higher, early on August 21.

Slowly executing a small counter-clockwise loop, Hilary underwent a Fujiwhara interaction with Tropical Storm Irwin which was several hundred miles southeast.

[10] Later that day, the thunderstorm activity became partially exposed from the center,[11] and on August 23, Hilary was downgraded to a tropical storm due to lack of organization.

[12] The interaction continued to weaken Hilary, leaving it with little thunderstorm activity and winds of just 40 mph (60 km/h) on August 24, before resuming a northerly motion.

[16] The outer bands of Hurricane Hilary also brought localized downpours to parts of California, resulting in flash floods.