(Adds details on Pemex operations, storm location)
MEXICO CITY, June 3 (Reuters) - Tropical Storm Boris drew closer to the southern Pacific coast of Mexico on Tuesday night, churning northward toward the largest refinery of national oil company Pemex, Salina Cruz.
A Pemex spokesperson said the Salina Cruz refinery, where Pemex can refine up to 330,000 barrels of crude per day, was operating normally and that it did not expect any disruption on Wednesday.
The U.S. National Hurricane Center (NHC) said Boris was heading north at 5 miles per hour (7 km per hour) and was about 85 miles (140 km) southeast of Salina Cruz.
Blowing maximum sustained winds of 40 mph (65 kph), the storm was expected to make landfall early Wednesday morning.
The Miami-based NHC said a tropical storm warning was in effect from Salina Cruz in southern Oaxaca state south to Mexico's border with Guatemala.
Heavy rain hit Oaxaca on Tuesday, prompting classes to be canceled in some schools. (Reporting by David Alire Garcia)