It is just as well the Principality Stadium roof was open. It would have been difficult keeping a lid on Welsh celebrations.
As the rain poured down, so did the beers of joy; exuberant Wales fans spilling their pints from the middle and top tiers, so that even those with shelter from the storm were drenched.
Such was the delirium in the stands, nobody seemed to mind too much. A Grand Slam, a record third for head coach Warren Gatland, was something worth toasting.
The adulation for Wales' players was deafening and yet the crowd scaled new, ear-splitting levels of noise when captain Alun Wyn Jones appeared on the big screen for his post-match interview.
His collar ripped and chest heaving after another monumental performance, Jones spoke of his pride and paid tribute to his team-mates and Gatland.
Just a minute later, though, his attention had already turned to the World Cup, finishing by saying: "We've just put a big target on our backs."
It was a moment which typified Jones, a prodigiously driven and single-minded leader.
Even after a heroic display which further underlined his legendary status, the triple Grand Slam winner was setting his sights on the next target.
He and Gatland set the tone for this Welsh side: Jones on the pitch with performances as consistent as they are intense, Gatland off it with his forensically detailed strategies and bullish confidence.
Among the ticker tape and fireworks, the fact this victory extended Wales' record winning run to 14 matches and saw them leapfrog Ireland into second in the world rankings felt like a mere footnote.
Jones and Gatland will have known - there are not many details which pass them by - but even these arch pragmatists allowed themselves to celebrate.
"I don't know if I'm going soft in my old age or whether it's because I've become a father, but when you see young men come into the side and grow over a nine week period it's brilliant," said Jones.
Gatland, the hardy, bulky former hooker, seemed to be softening too.
As he walked around the Principality Stadium pitch during the celebrations, there was a wistful quality to the way in which the New Zealander admired his surroundings, drinking in the atmosphere for one last time after a 50th and final Six Nations match in charge of Wales.
At one point, Gatland - normally a man whose inscrutability would dupe the most seasoned poker player - even appeared to wipe away a tear. Or was it the rain?
"It was the rain I think," he said afterwards with a laugh.
"There was no doubt I was reasonably emotional afterwards. It's great. I get such a buzz watching those guys lifting the trophy and celebrate.
"That's' what it's all about. The great thing about winning the last games of campaigns is you get to enjoy the next couple of months.
"Before our next game we can have a bit of a break and start planning and preparing for the World Cup and warm-up games."
Planning. There was that word again. Even after admitting to feeling emotional, that steely practicality which has been so important to Gatland's success remained.
Wales' coaches usually hold a meeting on the Tuesday morning after their final match to analyse the campaign in detail.
But in these exceptional circumstances, even Gatland was willing to change his plans.
"We are meeting as a staff on Tuesday and we've cancelled that," he said.
"We're meeting for lunch now and a long afternoon because it is our last time together and there is nothing to review of the Six Nations.
"I can sum it up in two words. Pretty good. That's the review over."
'Highlight of my career' - Wales players react
Fly-half Gareth Anscombe: "It's hard to put into words what this means, we've worked incredibly hard over the last year. We have a habit of winning. It's a special group and we worked hard for each other.
"We wanted to enjoy it. We're in the best stadium in the world in front of our people and we wanted to take the game to them.
"It hasn't all been smooth sailing. For me it's a day and weekend to remember for Welsh rugby."
Try-scorer Hadleigh Parkes: "The two home games we have had have been amazing. The support we get is amazing. We really enjoy it. To go and do it like that is amazing.
"Everyone is good mates, we want to work hard for each other and we managed to get some points today. It was good to get the win.
"I am sure the streets in Cardiff will love it. We will enjoy it tonight and the next little while."
Wales blind-side Josh Navidi: "It was fantastic. This will stay with me for many years and it is the highlight of my career so far.
"Winning all your games is an achievement and it was great to finish on a high. When you are on a 14-game winning streak it's pretty special.
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"We have won the Grand Slam and that is amazing. It's nice to earn the medal myself because I have been in squads before that have won the Six Nations
"We can enjoy tonight and then focus on the future."
Flanker Justin Tipuric: "The changing room was full of happiness and noise afterwards and rightly so.
"There is a lot of hard work that has gone in the last eight weeks we have been together and to finish the tournament in the manner we did was pleasing.
"At the start of the tournament Warren Gatland said if we beat France we would go on and win the Grand Slam and he was not wrong.
"The best way to sum Warren up is that he knows how to win. The coaches have said when you are in winning form you find it hard to lose."
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