Tokyo: Sifan Hassan bagged the first of what she hopes will be an unprecedented hat-trick of track golds while Kenya's astonishing run of victories in the men's steeplechase ended as boiling sun gave way to torrential rain at the Olympic athletics on Monday.
The conditions caused a delay to the field events, Valarie Allman eventually winning the women's discus with her opening throw - an unlikely source for the United States' first athletics gold of the Games.
If Dutchwoman Hassan is going to bag her remarkable treble, nobody can say she had it easy as she began the day by falling on the last lap of her 1,500 metres heat, only to spring up and charge through the field to finish first.
Fuelled by caffeine, she returned to the track in the evening and was in total control of a slowly-run 5,000 metres, sitting in the pack before unleashing her trademark last-lap burst. Kenyan Hellen Obiri held her for half a lap but slipped back and had to settle for a second successive silver.
Hassan will return to 1,500 for the semifinals, with the 10,000m, the event she held the world record in for two days in June, the final part of the jigsaw.
"It has been an amazing day. When I fell down and had to jump up I felt like I was using so much energy," she said.
"Before the race here I didn't even care. I was so tired. Without coffee I would never be Olympic champion."
The only occasions Kenya have not won the steeplechase gold since 1968 were when they boycotted the 1976 and '80 Games and they were bidding to make it 10 in a row on Monday.
However, the stranglehold was finally broken, emphatically, as Morocco's Soufiane El Bakkali took the title.
El Bakkali, fourth in the 2016 Olympics, spoiled up what was supposed to be an East African showdown with a surging final lap to win in 8:08.90 minutes after Ethiopian Lamecha Girma had made most of the running but ended with silver.
Benjamin Kigen's bronze medal was little consolation for Kenya.
"I'm so used to seeing Kenyans win, it's a big accomplishment for me," said El Bakkali.
"I have tried so many times to compare myself with the Kenyans and Ethiopians to see whether I could reach this gold, and I did."
Defending champion Elaine Thompson-Herah and fellow Jamaican Shelly-Ann Fraser-Pryce, one and two in the 100m final, look in great shape to repeat that in the 200m after impressive qualifying performances.
Thompson-Herah, seeking a second successive Olympic sprint double after bagging the 100m gold on Saturday, matched her personal best of 21.66 seconds, while Fraser-Pryce cruised to 22.13.
There was mixed news for the last two winners of the men's 400m as 2012 champion Kirani James of Grenada looked back to his best with the fastest semi-final time but defending champion and world-record holder Wayde van Niekerk of South Africa failed to progress after a long run of injuries.
The women's 400m hurdles showdown is on as American rivals Dalilah Muhammad and Sydney McLaughin safely negotiated a sodden track to win their heats and set up a final where the world record, recently taken from Muhammad by McLaughin, will be under threat.
The morning session produced its share of thrills and spills as Puerto Rico's Jasmine Camacho-Quinn impressively took the 100 metres hurdles - her country's first-ever athletics gold - and Miltiadis Tentoglou of Greece won men's long jump with his final leap, his country's first medal in the event.
Tentoglou's leap of 8.41 metres put him level with Cuba's Juan Miguel Echevarria but his next best effort was superior, securing the gold.