Hurricane Carlos has weakened slightly but is expected to regain punch, hovering over the Pacific Ocean off Mexico.
The US National Hurricane Centre said the eye of the Category 1 storm is about 80 miles south-southwest of Acapulco with top sustained winds of 74mph.
A hurricane warning extends from Punta San Telmo to Tecpan de Galean and a hurricane watch from west of Punta San Telmo to Manzanillo. A tropical storm warning runs east of Tecpan de Galeana to Punta Maldonado.
Carlos could eventually dump six to 10 inches of rain or more across four south-west Mexican states and cause life-threatening flash floods and mudslides, forecasters said.
It is the third hurricane of the 2015 eastern Pacific season.