John was upgraded to a Category 1 hurricane from a tropical storm Thursday morning and was expected to further strengthen before again making landfall in Mexico on Friday, meteorologists said.

The storm, which wreaked havoc in Mexico earlier this week, killing at least two people, could peak at Category 2 strength as it approaches and moves along the coast of southwestern Mexico or just inland, the National Hurricane Center said. It will then quickly weaken into a depression by nightfall.

A hurricane warning, which means that hurricane conditions were expected within 36 hours, was active from Tecpan de Galeana to Punta San Telmo. A tropical storm warning was active from Punta Maldonado to Tecpan de Galeana and from Punta San Telmo to Manzanillo, forecasters said.

On Monday, John intensified from a tropical storm to a Category 3 hurricane, bringing maximum sustained winds of about 120 miles per hour as it struck land. It fell apart over Mexico on Tuesday afternoon, but forecasters warned that flash flooding was possible in south and southwestern Mexico for several more days.

By Tuesday morning, the storm had dumped more than 10 inches of rain on parts of Guerrero and Oaxaca, two of the country’s poorest states, according to local authorities.

On Wednesday evening, the storm’s winds had increased to 70 m.p.h. as it moved back toward land. Through Friday, the storm was expected to bring an additional 10 to 20 inches of rain across the Mexican states of Guerrero, Oaxaca, coastal Chiapas and coastal Michoacán, forecasters said.

The heavy rainfall will likely produce “catastrophic, life-threatening flash flooding and mudslides” along four states on Mexico’s coast, according to the center.

Ahead of the storm, President Andrés Manuel López Obrador of Mexico urged residents in affected areas to “seek higher ground, protect yourselves and do not forget that life is the most important thing; material things can be replaced..”