The Borussia Dortmund attacker says the climate will put European sides at an immediate disadvantage, but is buoyed by the news that Manuel Neuer and Philipp Lahm are both fit.
Joachim Low's side reached the semifinals in South Africa four years ago but the Borussia Dortmund attacker feels that the odds are stacked against Die Mannschaft going all the way this time around - despite their best efforts to acclimatize in the run-up to the tournament.
"First of all, I associate with Brazil with the World Cup and football - but also the heat, which will play a major role," Reus reasoned. "We will prepare very well and are working hard to achieve the necessary strength and conditioning.
"But the favorites? It's the South Americans, due to the conditions, which will give them an advantage."
However, Reus has been buoyed by the news that both injury doubts Manuel Neuer (shoulder ligaments) and Philipp Lahm (bruised ankle) have been given the all-clear to play in Brazil.
"They have made a very positive impression [since joining up with the squad]," he revealed. "This is very important because they are very important players for us."
Germany has been drawn in Group G alongside Ghana, United States and Portugal.