PORTLAND — It took more than two hours and the patience to ride out cold spell after cold spell Wednesday night, but a throng of 5,909 at Cross Insurance Arena finally got its lungs into the Boston Celtics’ return to Maine.

Lou Williams spoiled the party with one, floating 3-pointer. Williams’ bomb with six-tenths of a second remaining in regulation descended through the hoop as he fell away from the basket and landed with a fist pump, giving the Toronto Raptors a 92-89 exhibition victory.

Jordan Hamilton scored 16 points and Williams 15 for Toronto, which never trailed after the four-minute mark of the opening quarter. Terrence Ross and Patrick Patterson added 12 points apiece for the Raptors.

“The crowd was great. I’m sorry for them that we struggled to put the ball in the ocean the first three quarters,” Celtics coach Brad Stevens said. “It was a struggle. I just hate losing. Preseason, regular season, whatever.”

Jared Sullinger’s potential game-tying 3-pointer rattled in and out at the horn.

Boston scored nine unanswered points to tie it at 89, beginning with Avery Bradley’s steal and fast break layup at the 1:49 mark.

Kelly Olynyk’s putback sliced the deficit to five, and after getting fouled beyond the arc, rookie Marcus Smart made all three resulting free throws.

“It was big for me to be put in that situation,” said Smart, who finished with 11 points in just under 30 minutes. “For the team aspect, it was big for them to see they can trust me in that situation.”

Jeff Green, seeing his first action after missing the first four games of the exhibition slate, grabbed the rebound of Greivis Vasquez’s miss with 14 seconds remaining.

Bradley’s 12-foot jumper from Olynyk tied it.

“It was good to be out there,” said Green. “I haven’t been able to play at all the past two weeks. I was dead tired, but once I get my legs under me I’ll be fine.”

Nobody’s feet were quick enough to rotate and cover Williams, who rained down the Raptors’ sixth 3-pointer of a frosty night at both ends to win it.

“Boston is such a quick team,” Toronto coach Dwane Casey said. “They’re like a one-man press with their guards, and I thought Lou did a good job with handling that.”

“Jordan Hamilton stepped back and hit one right in front of our bench early in the fourth quarter, and then Vasquez hit one,” Stevens added. “Williams is a good shooter. They made the contested ones when it mattered.”

Playing without Rajon Rondo and getting only nine points and five rebounds from Green, the Celtics spent much of the night exploring the options deeper down their bench.

Marcus Thornton scored 12 of his team-high 17 points in the fourth quarter. Tyler Zeller was 6-for-6 from the field and matched Bradley with 13 points.

“I’m getting more comfortable out there,” Zeller said. “The guys got me the ball for layups and made my job a lot easier.”

Smart and Evan Turner each added 11 points for Boston. Turner rescued the Celtics’ stagnant offense with seven points in the third quarter before he was assessed back-to-back technicals and ejected with 2:09 remaining in the period.

Asked if he heard what Turner said and if he deserved the unusual early departure in the preseason, Stevens said, “Yes, I believe so,” with a wry smile.

It was a rough third quarter for the Celtics. Boston scored only two points in the first 7:42 and lost Green for several minutes after he was poked in the eye on a drive to the basket.

Green stayed on the court to attempt the ensuing free throws. He missed both and was in obvious discomfort, squinting as he did so.

On Boston’s next possession, the Celtics were forced to use a timeout to remove Green from the game. He returned for two stints in the fourth and was on the floor at the end of the game.

“Yeah, I’m good. I can see. It just got real, real blurry when I got hit,” Green said. “It took about 15 to 20 minutes for it to clear, but I’m straight.”

After the Turner ejection, Toronto capped the quarter with a 6-0 run for a 68-56 lead.

“Everybody played hard, both teams,” Hamilton said. “We had some turnovers, but you know we came back and did some good things on both ends of the floor.”

The Celtics overcame a dreadful shooting start and uninspired early defense to rally from a double-digit deficit to a 43-43 tie at half.

Boston’s final lead of the night was 9-8 on a Bradley jumper with 5:07 to go in the first.

“It’s the first time we’ve had an end-of-game situation,” Stevens said. “They executed, got stops, got rebounds, made shots. I thought they played pretty well at the end, which is encouraging.”

And Maine responded with its loudest noise of the night.

“The atmosphere was great. The fans were great,” Green said. “That’s a Boston crowd, right there.”