The major storm threatens to unleash destructive winds, flash floods and a dangerous storm surge near where the eye crashes ashore.
The Miami-based centre reported Erick was about 110km west-southwest of Puerto Angel, Mexico, and about 145km southeast of Punta Maldonado, Mexico, early on Thursday.
The storm had maximum sustained winds of 230km/h and was moving northwest at 15km/h.
A hurricane is defined as category four when wind speeds reach 209-251km/h.
Late on Wednesday, Erick's projected path crept south, closer to the resort city of Puerto Escondido in Oaxaca state, and centred on a sparsely populated stretch of coastline between the Oaxacan resort and Acapulco to the northwest.
President Claudia Sheinbaum said in a video message Wednesday night that all activities in the region were suspended and she urged people to stay in their homes or to move to shelters if they lived in low-lying areas.
Waves were crashing onto the esplanade in Puerto Escondido by nightfall, swamping wooden fishing boats that had been pulled up there for safety.
The beach disappeared under pounding waves and the rising tide had already reached the interiors of some waterfront restaurants.
Last-minute purchases ended at nightfall as stores closed and the streets emptied.
The storm's course shift could be welcome relief for residents of storm-battered Acapulco.
The city of nearly one million was devastated in October 2023 by Hurricane Otis, a category five hurricane that rapidly intensified and caught many unprepared.
At least 52 people died in Otis and the storm severely damaged almost all of the resort's hotels.
Forecasters said Erick was expected to lash Mexico's Pacific coast with heavy rain, strong winds and a fierce storm surge.
Rains of up to 40 centimetres could fall across the Mexican states of Oaxaca and Guerrero, with lesser totals in Chiapas, Michoacan, Colima and Jalisco states, the center's advisory said.
The rainfall threatened flooding and mudslides, especially in areas with steep terrain.
A hurricane warning was in effect from Acapulco to Puerto Angel.
A hurricane warning means hurricane conditions are expected in the area, and preparations to protect life and property should be rushed to completion, according to the hurricane centre advisory.
