The calendar may say December, but for many Inner Harbor attractions it will soon seem like a summer day at the peak of the tourist season.

No matter what business has been like the rest of the year, local Baltimore attractions can count on a boost in attendance between Christmas and New Year's when schools are closed.

"The day after Christmas, we just get a ton of people," said Michelle Winner, a spokeswoman for Port Discovery, Baltimore's children's museum.

"We have a lot of tourists coming in because they're visiting family," Winner said. "There are lots of happy kids and tired parents."

Records from 2001 show that the number of visitors to Port Discovery during Dec. 26-Dec. 31 was up 43 percent over other weeks in December, according to Winner.

"There's always a spike in visits to museums over the holidays," said Edward H. Able, president and chief executive of the Washington-based American Association of Museums, which has more than 3,000 members in the United States and beyond.

"It's been that way for the last couple decades at least," Able said. "Families are together, and they're looking for things to do together."

Museums across the country develop their programming with the holidays firmly in mind, he said.

This year, the Maryland Science Center has timed the opening of The Lion King at its IMAX theater to coincide with the holiday period, and the popular Grossology exhibit has been held over, said Christopher Cropper, senior director of marketing.

Movie and planetarium shows are being added to meet the anticipated demand.

"Historically, the Inner Harbor attractions have always been a place where families have gotten together during the holidays," Cropper said.

"We actually do between 30 and 40 percent of our monthly projection for December during that time between Christmas Eve and New Year's Eve," he said.

"You're talking about five days out of 30 bringing in a third of your business."

It's a pattern that the National Aquarium at Baltimore has tracked year after year.

"Within December, that week can triple some of the other weeks," said Andrea Butler, a spokeswoman for the aquarium.

"Winter break attendance is comparable to summer weekdays," Butler explained. "But winter break attendance is more local and regional compared with the mix we have in the summer - the out-of-market crowds."

Aquarium members also come during those days, she said.

"I think it symbolizes that they have family in town, and they want to show their local pride in the aquarium," Butler said.

"It's a family activity. People have more leisure time then."