The Gulf region faces the threat of tropical storms and hurricanes every summer and fall, but there is an added complication this year. Heavy snowfall on the Great Plains over the winter and relentless rains in the spring have already swollen the region’s bayous and the Mississippi River and its tributaries, which drain to the Gulf. That has left the region’s levee systems with much less room than usual to absorb additional water.”

With days of heavy rain on the way, the Mississippi River is expected to crest at New Orleans this weekend at close to 20 feet. The city’s levees along the river are between 20 and 25 feet high, according to Ricky Boyett, the spokesman for the Army Corps of Engineers in the New Orleans District.

“We’ll be getting to the top of some of our lower levees if the forecast holds,” he said, cautioning that it was still early to lock in a prediction.

Mr. Boyett said the Army’s team of engineers was trying to identify any low areas and reinforce them. “We’re not concerned with integrity” of the levees, he said, only with how high the water rises.

Hurricanes have struck Louisiana in July three times in 168 years of record-keeping. All have occurred in the last 40 years. Experts say that trend can be attributed in part to climate change warming the waters of the Gulf of Mexico.

New Orleans has always been a place where heavy rains fell, but the inundations in recent days and what is expected from the latest storm are consistent with climate change’s effects: warmer air holds more moisture, which then comes down in the form of extremely heavy rainfall.

Loyola University New Orleans, which was flooded in spots on Wednesday, announced that it would cancel classes and close its campus on Thursday and Friday, as other colleges in the city have.

“If this were occurring during the more crowded fall semester, we might try to stay open tomorrow,” Tania Tetlow, the president of Loyola, said in a statement to employees and students. “But I’m conscious of the fact that many of you are recovering from this morning and have work to do to get ready for the weather ahead.”