The “10 best days of summer” are now a long weekend.

The Minneapolis Aquatennial has slashed its two-week run of festivities to four days this year — July 22-25. Organizers say the drastic change is necessary to keep the summer celebration relevant and encourage more participation.

Though many signature events will remain under the compressed schedule, the popular milk carton races on Lake Calhoun are the most notable casualty.

The move by the Minneapolis Downtown Council comes on the heels of an unpopular decision last year to retool its other major event, the wintertime Holidazzle parade and carnival, into an outdoor marketplace on Nicollet Mall.

The Aquatennial has been celebrating Minneapolis’ love affair with its lakes and the Mississippi River since 1940, with parades, fireworks and water activities.

Now approaching the festival’s 76th year, Downtown Council officials said the shortened the time frame will let it “refresh the Aquatennial experience” at a time when Minnesota families are trying to squeeze as much out of summer as possible.

“What we’re trying to do is capture that same attendance that would historically come to those flagship events, and get them to participate in more activities and make it easier for them to do that,” said Leah Wong, Aquatennial festival director and vice president of events and marketing of the Minneapolis Downtown Council.

“While people have historically loved the events, it has been a challenge because they’ve had to reserve two weekends plus a full week in the summer — when, as you know, our summers are precious.”

The cuts already are causing consternation among longtime fans, but the move toward shorter civic festivals with fewer activities is consistent with a nationwide trend, said Doug Spong, president of the Spong advertising agency and a member of the Downtown Council.

“It’s not just a Minneapolis thing, it’s not just the Aquatennial,” he said. “It’s very much in keeping with legacy festivals that have been around for years. They compete for the time and attention with other festivals that are relatively new.”

The CenterPoint Energy Torchlight Parade will still begin the event and the Target-sponsored fireworks show will be the grand finale.

Other events, such as the 5K race, riverfront ski show, tennis tournament and coronation of “royalties,” will remain. A lineup of new events will be rolled out over the next few weeks, Wong said.

Some Minnesotans already are mourning the loss of the Aquatennial’s “Beach Bash,” which included the sand castle contest and milk carton race, which was first part of the Aquatennial in 1971.

The feedback on Facebook and other social media sites was pointed:

“Boo to a shortened Aquatennial!” wrote Danielle Wojdyla. “This is one of the highlights of living in Minneapolis, including the milk carton boat races!”

Wojdyla asked the organizers to reconsider: “You have many disappointed fans.”

Lee Ann Gustafson also groused about the short notice. “If you are going to cancel time-honored events like these you should give a year’s notice,” she said. “What about all the families and groups that have already started work on their milk carton boats and have been saving all year to do so?’’

Even Spong, who applauded the council’s decision to “break with tradition,” was baffled by the sinking of the milk crate races.

“It’s what was unique about Minneapolis,” he said. “It was different, it was quirky, it was hilarious. You didn’t care who won or lost, you just looked at the inventiveness of the designers.”

Wong said the decision was a response to changing times, not due to a drop in sponsorship or crowd interest. The event is self-supporting through corporate sponsorship and volunteers, she said.

Wong wouldn’t provide budget details for the event but said there were no cost savings to collapsing its schedule, dubbed “the 10 best days of summer.”

Changes to the Aquatennial and Holidazzle are part of the council’s larger strategy to expand its programing from two principal events to a year-round approach to create a more “consistently compelling downtown experience.”