The planning and execution have taken weeks. Months, even. You can’t air condition a barn like Williams Arena by plugging in a few window units and call it a game.

When the top-seeded Lynx open the WNBA semifinals Tuesday at Williams — their second temporary home this season — the Barn will be cooler than the other side of coach Cheryl Reeve’s pillow.

But it wasn’t easy.

This is a 1928 building hosting a 21st-century event. It can get as hot as Hades inside, when the house is full, even if it’s cool outside. And don’t get Wolves and Lynx President Chris Wright started on the logistics of hosting two teams, a media contingent, league officials and broadcast partners. That’s a size-12 assignment being pushed into a relatively tiny footprint.

“I don’t know of another professional sports franchise in the country that has gone through something like this, to take a game into a building that didn’t have something that the players and league needed, and have to execute all of that,” Wright said.

But it starts with air conditioning.

The Lynx became aware months ago they were going to have to move out of Xcel Energy Center, which was their home this season while Target Center was being renovated.

But where to go?

The Lynx looked at Mariucci Arena, but it was booked. Wright said the team even reserved dates at civic centers in Mankato and Rochester.

But owner Glen Taylor wanted the games to stay in the Twin Cities, and so attention turned to Williams Arena — a hot arena that needed cooling down.

An expensive undertaking

The Lynx hired Aggreko, a company that specializes in air conditioning difficult places, such as hospitality tents at major golf events. It sent a team of engineers from Houston to Minneapolis to examine Williams Arena, which needed to be kept between 61 and 71 degrees during a game.

Problems: Converting the heating system into a cooling system. Adjusting the existing ductwork to make sure Williams is cooled but the adjoining Sports Pavilion isn’t. Making sure that whatever system was installed could handle the body heat of thousands of fans and that all the cool air that escapes doesn’t affect arena temps.

The answer: an enormous system of chillers, fans and pumps.

“It sort of reminds me of the movie ‘ET’, ” Wright said. “We’re building this massive plant on the outside of the building that will force cold air through the air-handling system, through the ceiling, through the louvers on the outside of the building.”

It isn’t cheap. Should the Lynx play the maximum six home games in the semifinals and finals, it will cost upward of $1 million.

A home-court feel

The preparations were extensive. In a deal negotiated with the university, the Gophers “M’’ will remain at center court but much of the rest of the signage will be covered by signs that reflect league- and Lynx-related sponsors.

“We’ll dress up the court to create the Lynx feel, the Lynx brand, so our women feel this is a home court,” Wright said.

Williams has a capacity just over 14,000. In last season’s semifinals against Phoenix, the Lynx averaged 9,322 in two games. In three games vs. L.A. in the finals that jumped to 14,789, including 19,423 in Game 5. Wright said there is a plan in place to offer $6 upper-level tickets to University of Minnesota students for any game that isn’t sold out.

It appears the Lynx will occupy the Gophers women’s locker room. ESPN and ABC will likely take the men’s locker room. The Lynx opponent will use the traditional visitor’s locker room.

The club room at the arena also will be used, and possibly even temporarily subdivided, to make room for everyone.

Until then, the Lynx will work at their practice facility Wednesday through Friday, take Saturday off, then practice at Williams Arena on Sunday and Monday.

Former Gophers star Lindsay Whalen, not surprisingly, is thrilled to be playing there. But it will take some time to adjust to the sightlines and the arena’s elevated court. Other than Whalen, center Sylvia Fowles and guard Seimone Augustus both played in Williams once. It was in December 2004, when top-ranked Louisiana State played the Gophers. Augustus scored 22 points and Fowles 15 in LSU’s 75-67 victory on a night former Lynx player Janel McCarville went off for 31 points and 13 rebounds.

“We’ll have those two practices, and our gameday shoot-around,” Reeve said. “We’ll get three times in there before playing. As long as we have coaches locker rooms, players locker rooms and the trainers have what they need, we’re in good shape.”