The rain delay Sunday night at Madison Square Garden — yes, that’s right — would have been far more costly for the Knicks than the one the Mets dealt with earlier in the day.

While the Knicks were in the process of flushing an 18-point lead in the second half, the game was delayed for 14 minutes due to water falling from the ceiling onto the court.

The Raptors surged ahead soon after play resumed, but RJ Barrett’s 3-pointer with 34.3 seconds remaining and Julius Randle’s late insurance free throws helped pull out a critical 102-96 victory for Tom Thibodeau’s team.

“I thought it was baseball, with that little rain delay,” Thibodeau said. “Those things happen and you can’t allow yourself to get distracted. I think we still had a 10-point lead at that point, and it sort of stalled the game. But there’s nothing you can do about it.

“Whatever you have to do to pull it out, that’s what you have to do. … And we found a way at the end. I liked that we had the mental toughness to work our way through it and pull it out in the end. But I think we’re capable of playing better than we did.”

The eighth-place Knicks’ first win in 10 games against the Raptors since November 2017 was a significant one for them in the Eastern Conference standings, increasing their cushion over No. 11 Toronto to six games with 18 remaining. The top six teams in each conference automatically qualify for postseason play, with teams seven through 10 subjected to play-in scenarios.

“We’ve been in tough stretches, had tough games, tough breaks, close calls, all season long, where we’ve been fighting in close games and they haven’t gone our way,” Randle said. “So it’s good to mentally get over that hump.”

Randle netted a team-high 26 points and Barrett scored 19 for the Knicks, who have won consecutive tight games at the wire — following Friday’s OT thriller against Memphis — after dropping five of their previous six. They will play again Monday at home against the Lakers, who remain without injured stars LeBron James and Anthony Davis.

Nerlens Noel contributed nine points, 13 rebounds and four blocked shots for the Knicks (27-27). Gary Trent Jr. scored 23 points and Kyle Lowry added 19 for a Raptors squad (21-33) that played without Fred VanVleet (hip) and OG Anunoby (rest).

Randle sank two free throws with 13.4 seconds remaining in the second quarter as the Knicks carried a 56-42 lead into intermission. Barrett and Reggie Bullock (10 points) connected from downtown early in the third to extend the Knicks’ advantage to 18.

“You see that in the league now, no lead is safe,” Thibodeau said.

The 14-minute rain delay came at the 3:58 mark of the third, with the Knicks leading by 10, due to what the team called “a small drip from the rain,” coming from the ceiling. After the problem was rectified, the Raptors closed to within two points, 78-76, by the end of the quarter on 3-pointers by Trent and Chris Boucher.

Toronto’s 37-15 surge overall enabled them to grab an 87-83 advantage on Rodney Hood’s 3-pointer with seven minutes remaining in the fourth.

The Knicks netted the next nine points to regain the lead, however, including a drive by Barrett and a straightaway 3-pointer by Alec Burks for a 92-87 lead with 3:24 remaining.

Barrett’s right-corner 3 in the final minute extended a one-point cushion to four. After Pascal Siakim was called for traveling with a chance to tie the score, Randle sank four straight free throws in the final 10 seconds to seal the win.

“Even when we were down [in the fourth quarter] I just felt that we were gonna win the game,” said Randle, who added eight rebounds and five assists. “It was just time that we got over that hump and we did.”