Kangaroos coach Tim Sheens opted to cut short Wednesday's training session at Harrow School and Tamou, who was born in Auckland but plays his club rugby in North Queensland, was grateful to find shelter.
"We were just finishing up and it started hailing so the coach called it off and we all sprinted back to the changing rooms," Tamou told Press Association Sport.
"This is my first time over here. I think I have experienced this kind of weather before but it's been a while.
"The average temperature in Townsville right now might be around 30 to 33 degrees."
Temperatures are likely to only drop further in London ahead of the World Cup semi-final double-header at Wembley but Tamou expects the competition to be red hot when his side tackle the Fijiians.
Australia won 34-2 when the sides met in a group match in St Helens earlier this month but Tamou believes the Pacific Islanders have improved significantly since that day.
"They have a physical side," he said. "I watched them against England and they were a whole different team. It was just a shame they let up early in the second half and England ran away with it.
"But they have a big physical side and they do have some class in the backs, too. They are definitely going to be a more improved side from the first time we played them.
"With it being a semi-final, they will definitely step up. We really need to bring our A game and be ready for them."
Tamou is acutely aware of the threat posed by the Fijian pack, which will be led by the Sims brothers, Ashton and Tariq, who are team-mates of his at the Cowboys.
"They're passionate boys," Tamou said. "They're passionate about where they're from and they're passionate about their families.
"They leave nothing on the field, especially Ashton. He gets right into it, he's very emotional. He'll be one of their go-forward players this weekend."
Sheens is forced to make at least one change to the team that demolished the USA 62-0 in last Saturday's quarter-final, switching Greg Inglis to full-back in place of the injured Billy Slater.
Brent Tate is set for a recall to plug the gap at centre while the coach's only dilemma will be the make-up of his bench.
Tamou, who went into the tournament with just three caps under his belt, has started all four matches so far and is delighted there is no let-up for him.
"I'm glad it's happened this way," he said. "It's hard to watch the boys play when you're sitting on the bench. You get the itchy feet.
"Sheensy has got confidence in me and I'm pretty good with my body. I do all the little things right to recover and I'm pretty happy to go right through the tournament and hopefully play the final if we make it."