With the brooding clouds above becoming as dark as a blackbird's oxter, while they gloomily gathered in preparation to unleash the kind of fearsome downpour that would've had Noah in a lather, the rampaging Dane putted out for a birdie on the 18th in a superbly assembled 10-under 62.
No sooner had he finished scribbling his signature on to his course-record-setting card, the klaxon honked in the background and play was suspended. At least Bjorn was home and dry at the BMW PGA Championship as he finished two shots clear of Shane Lowry, the Irishman, on a stop-start day that left 11 groups still needing to finish their opening rounds.
Having eased to the turn in three-under, it was all relatively quiet on the West Course front until Bjorn unleashed the heavy artillery and came thundering home in just 30 blows. It really was a magnificent seven-under; a back-nine illuminated by a purposeful and profitable two, three, three run - birdie, birdie, eagle - from the 10th. With no wind, no sun and overnight rain providing an invitingly receptive lay out for the early starters, the conditions for Bjorn's golfing assault were ideal.
This has never been his ideal venue, mind you. Bjorn may have been a resident on the plush, leafy Wentworth estate for nine years but the West Course seemed to be a neighbour that could easily have been given an anti-social behaviour order. The 43-year-old has managed just one top-10 here since 1996. If he was a doubting Thomas about this neck of the woods, then it certainly didn't show yesterday.
While Sergio Garcia withdrew with a dodgy knee, Bjorn brought the 'West' to its knees. "The best one, absolutely," he said when asked to rate where the round ranked on his all-time hit parade. "You shoot great rounds of golf in your career but to shoot 62 on this course? You can't ask for much more."
The omens look good, too. The last time he blasted a 62 was in the Omega European Masters of 2011 and he went on to win it. He reclaimed that particular crown last season while he notched European Tour victory No.15 earlier this year when he won the Nedbank Golf Challenge. A return to the Ryder Cup fray for the first time in 12 years at Gleneagles this September now beckons. From battling mental demons and suffering a dramatic loss of form, Bjorn has been reborn as he hurtles through his 40s.
"I have travelled with my golf clubs since I was 14 and sometimes you forget why you love the game and it becomes hard work," he reflected. "This tour can be a lonely, tough place when you're not playing well.
"I just had a hard look at myself and then you realise that it's the only thing you really want to do. It's about hard work and a determination not to let a golf career fade away. I feel great about tour life now. I think you get to a stage where you can kind of see the end so you just want to enjoy the last bit."
Enjoyment is not something Rory McIlroy has experienced much of this week, given the much-publicised palaver surrounding his break-up with his fiancée, Caroline Wozniacki. The Northern Irishman was eager to get cracking and find some kind of solitude inside the ropes but even that was delayed when the hooter sounded to call a halt to proceedings just 15 minutes before he was due to tee off.
Once he got going, McIlroy put all of his troubles behind for a few hours at least with a spirited display that was burnished by a brace of eagles in a four-under 68. He holed a wedge from 130 yards at the seventh for a two before smacking a 5-iron from 203 yards to within a foot on the 12th.
In the uncomfortable, awkward circumstances, it was an admirable effort around a course that has not produced many memorable moments for him in recent seasons. "At times it was difficult; I wouldn't be human if I didn't find it tough," he said. "I just wanted to bury my head in the golf and I thought I did that very well."
Amid the fevered scrutiny of these high-speed, online times, McIlroy has tried to find a way to avoid all the attention. "I've not turned my phone on for a few days and I've given my laptop away," he added, as he turned himself into a technological hermit. "I've been kind of living in the 70s."
He can take considerable comfort from the fact that he was shooting in the 60s, though.