Three sirens blared around my hotel room with a woman calling out a warning in Japanese.
Within seconds, the entire building was shaking, swaying to and fro.
My first reaction was to wonder how I had ended up asleep on a boat. The second reaction was that Typhoon Jebi, which had battered central Japan this week, had made landfall in the northern Japanese island of Hokkaido, where I was currently on vacation.
But upon checking my phone - the source of the blaring wake-up calls at 3.08am - I realised it was an earthquake. Reports said the magnitude-6.7 quake had triggered landslides in some rural areas, causing houses to be buried.
The power did not go off immediately but several minutes later, which left me guessing as to whether this was a grid failure or a safety measure.
Later, in the glare of the early autumn sun, I would learn that despite the best efforts of generators and other auxiliary power sources, buildings all around central Sapporo, the capital of Hokkaido, had no electricity.
Or water. Toilets were not flushed and a long queue built up at the nearest Seicomart, one of the few 24-hour convenience stores in the area that decided to keep its doors open, as both locals and tourists stocked up on provisions.
But there was a general air of calm as road users continued to obey traffic rules despite the traffic lights not working, helped by wardens at busier intersections.
On less busy streets, motorists stopped for one another and pedestrians.
In fact, the only people panicking seemed to be tourists, who crowded around hotel reception desks asking incessantly for updates and assistance.
Even before 6am, men in business suits and women with full make-up on were headed to work, many on bicycles.
Salarymen and office ladies kept calm and carried on with their routines, unperturbed that just hours earlier, their beds had swayed like hammocks.
The only difference might have been that they had to leave for work earlier as public transport systems were shut down.
The ones who were most inconvenienced were perhaps travellers who were due to fly out of New Chitose Airport. They now had to find last-minute lodgings as they awaited rescheduled flights.
For me, there was nowhere to go except the nearby Nakajima Park. Here, it was a glorious day, with the warm sun beating down on dozens of children in the playground seemingly oblivious to the earthquake.
Maybe the inevitable thirst might spoil their mood, but right now, the greatest danger they faced was falling off the see-saw.