Don't mention the heat.That is the warning from Socceroos coach Holger Osieck to his players before they swap chilly Copenhagen for muggy Muscat.The national team is set for a spike in maximum temperature of almost 30 degrees for Friday's World Cup qualifier against Oman.Osieck tried to have the Muscat match pushed back from its 5pm (2300 AEST) kickoff time only to be rebuffed by FIFA.But now the starting time is locked in, the one thing certain to make Osieck hot under the collar is reminding him of the balmy weather."It is very tough to fight authorities and so we have to go from there," he said."But both teams will have to play in the conditions. The more you talk about it, the worse it gets."Osieck joked that talking about the heat could become "taboo" within the camp before the clash at Sultan Qaboos Sports Complex.The temperature is expected to cool a tad this week in Oman but the forecast is still for a top of 39 and nearly 50 per cent humidity on match day.Late afternoon can be one of the hottest times of the day in Muscat.Young Socceroos defender Matthew Spiranovic said the players had to draw on their experience from playing in the region."The weather is the biggest difference, I mean 40 degrees is not easy but we will be prepared off the field for it," said the Japan-based player."Players playing all around Asia. In Japan, Korea, UAE players are used to the summer we know what we need to do and how our bodies need to respond."We are all professional. We do not use it as an excuse."We have to do the job on the field and we will back ourselves against any team in Asia."Spiranovic said the most important thing was for players not to become flustered by the conditions."We have to control the game a bit more," he said."You have to be a bit clever in what you do."Australia warm-up for the clash against Oman in a friendly against Euro-bound Denmark in Copenhagen on Saturday evening (kickoff 0100 Sunday AEST).