Port and rail operations for grain shipping were beginning to return to normal in the upper U.S. Midwest after heavy rains drenched the region this week, shippers said.

Major exporter CHS Inc said it resumed grain loading operations at its Superior, Wisconsin terminal, a day after it halted loadings.

"Our Superior, Wisconsin, export terminal is back up and operating normally today," CHS spokeswoman Lani Jordan said.

The CHS facility is the largest grain terminal at the port with a storage capacity of 18 million bushels, according to the Duluth Seaway Port Authority.

The port, an export gateway on the western shore of Lake Superior that feeds into the St. Lawrence Seaway, spans the cities of Superior, Wisconsin, and Duluth, Minnesota.

Canadian National Railway plans to reopen some of its freight lines across Minnesota and northern Wisconsin this afternoon, said CN spokesman Patrick Waldron.

The railway runs about 25 trains a day across those lines, carrying bulk commodities including grains.

"Affected areas along the Iron Range, Rainy, and Superior and Two Harbors subdivisions will return to service," CN posted on its web site. "The southern portion of the Missabe subdivision is due to resume operations."

Heavy rains of 5 to 9 inches fell in the Duluth area, causing the worst flooding the city had seen in four decades, officials said. (Reuters)