Thunderstorms rolled through southeast Louisiana in waves Friday, with heavy rain flooding streets and sending people running for cover at the Jazz and Heritage Festival in New Orleans.

Cheryl Gerber / Associated Press

Crowds scurry for cover as rain begins to fall at the New Orleans Jazz and Heritage Festival, Friday, May 4, 2007, in New Orleans.

The downpour that began overnight led to scattered power outages and traffic tie-ups. Tornado warnings were issued for parishes north of Lake Pontchartrain as a line of storms crossed that area near midday.

Workers had to temporarily shut down pumps pushing water into the London Avenue Canal because it crept above safe levels, according to Vic Harris, a spokesman for the U.S. Army Corps of Engineers. The water quickly receded to safe levels, and the pumps were turned back on, he said.

"Now everything is copacetic," Harris said. "This is not an uncommon thing. We make those adjustments commonly when the water goes up."

At restaurants in New Orleans' Mid-City area, hard-hit by flooding during Hurricane Katrina more than 19 months ago, wait staff scurried about warning lunchtime patrons to move vehicles as water rose several inches on Canal Street. In Uptown New Orleans there were reports of water rising into some shops.

The street flooding, often seen with spring and summer storms in New Orleans, was minor by Katrina standards. The hurricane flooded 80 percent of New Orleans in August 2005, with some areas under up to 15 feet of water.

Louis Armstrong New Orleans International Airport reported some delays in takeoffs and landings as the heavy weather moved through. The 24-mile-long Lake Pontchartrain Causeway also was closed for a time.

At Jazz Fest, heavy rain cleared performers from outdoor stages, but jazz, blues and gospel performances continued in tents. Crowds packed in to escape the rain.

"There was no damage, no tents down, no injuries," said festival spokesman Matthew Goldman.

The festival turned electricity off to some areas as a precaution, Goldman said. Water on the grounds was near knee-deep for a time.

Up to five inches of rain was expected in some areas, and some underpasses were reported impassable. In suburban Jefferson Parish, authorities reported thoroughfares were flooded.

Southern University at New Orleans canceled classes for the day. The university, which was heavily damaged by Katrina, has been operating in temporary buildings constructed by the Federal Emergency Management Agency and the Army Corps of Engineers.

At Jazz Fest, heading its final weekend at the New Orleans Fair Grounds racetrack, rain dampened some but not all spirits.

"I spent $48 to stand in a tent and watch it rain," said Wayne Fillingin, 29, of Mobile, Ala. "So far I haven't seen anything and this is my first Jazz Fest ever."

Others were not as reticent about getting wet.

People in ponchos and with umbrellas were not the only ones that braved the storm. Judi LeBlanc and her friends took off their shoes and trotted happily through the downpour.

"We skipped school to be here," the 16-year-old said. "So we are definitely going to have fun no matter what."

At the Diamond Cutters' beer tent, both the workers and the customers stood in about a foot of water.

"You wouldn't believe it, but business is good," said Lena Stewart. "People are buying a dozen cans of beer at a time and taking it back to their friends."

At the Jazz Fest General Store plastic ponchos were a hot item at $5 each, umbrellas were $10.

"I was worried about a sun burn," said Val Washington, 47, of Dallas. "Now I'm worried about drowning. But there's still music, so it really isn't that bad."

(Copyright 2007 by The Associated Press. All Rights Reserved.)