Ireland captain Peter O'Mahony has acknowledged that the expected hot conditions in Houston will make Saturday's Test against the USA an even tougher examination for the visitors.
Temperatures were around 30 degrees centigrade when the Irish players trained on Tuesday and similar heat is likely on Saturday.
"It was tough, to be honest with you," said the Irish tour skipper.
"I was struggling a bit, the heat is oppressive with the humidity."
Both sets of management are discussing the prospect of following the lead of the British and Irish Lions in Hong Kong and introducing water breaks during the clash.
But O'Mahony, who will lead his country for the first time at the BBVA Stadium, does not want his players to use the weather as an excuse not to perform.
"We will be playing a bit later and both teams have to play in it so we have to get on with it."
O'Mahony, 23, believes the squad assembled by interim coach Les Kiss is bonding well despite the absence of Ireland's Lions tourists.
Wednesday's day off was spent at NASA's headquarters, while they met local NFL star JJ Watt who took them for a tour of the Reliant Stadium on Tuesday.
"I'm enjoying the trip so far. We had a good week in Carton (House) before we left, training has gone well and we are enjoying each other's company," O'Mahony explained.
"The USA are going into the Test thinking they're going to win it and we will do the same.
"It is not different to any other Test. It is the same as any other November international or Six Nations game."
Much has been made of the arrival of incoming head coach Joe Schmidt and the impact it will have on the Ireland players who are getting a chance to impress in the absence of the country's Lions.
But O'Mahony wants his team to ignore any potential distractions and play for the team.
"You are a professional representing yourself and your national team. It doesn't matter who is watching," he said.