Loew, who had spells in charge of FC Tirol and Austria Vienna earlier in his career, said Germany's opponents were now a bigger threat than they had been in previous meetings.
"Austria have improved and are more self-confident," he told reporters on Monday. "This time you can feel they mean it when they say they are sniffing a chance to beat Germany."
Loew has previously won 1-0 and 2-1 in Vienna as Germany coach.
"We have had big problems here before and there is always a heated atmosphere," he said. "The whole country is feverish about this match.
"They have learned a lot in terms of organisation and structure, they are a courageous and attacking team.
"The players who have come on the scene over the last few years all play abroad ... it used to be the other way round with foreign players moving to Austria so the players had less match practice," added Loew.
"They all have regular first team action, they are all important players in their clubs and there are eight or nine in tomorrow's starting lineup who play in Germany.
"The danger posed by players such as Marko Arnautovic (Werder Bremen) and Martin Harnik (VfB Stuttgart) has increased because they have asserted themselves in the Bundesliga," said Loew.
Austria have lost their last seven meetings with Germany and have not qualified for a tournament since the 1998 World Cup.
They were included automatically as co-hosts for Euro 2008 and were eliminated in the group stage but they are unbeaten this year under new coach Marcel Koller.
"We shouldn't underestimate ourselves," said Austria captain Christian Fuchs. "We have some good qualities.
"Losing to favourites Germany would not be the end of the world in a group where Austria are likely to fight for second place with Ireland and Sweden, with Kazakhstan and Faroe Islands as rank outsiders," added the Schalke 04 defender.
"Germany are not our only opponents," he said. "Even if we beat them it is only one game and we have to keep looking forward."
Loew said Germany had to be more clinical in front of goal.
"We have lots of shots but we have converted too few of them into goals," he said, referring to Friday's 3-0 win over the Faroes in a game where they could have trebled that tally.
"We have to talk it over and look to keep our concentration so we can put a decisive end to our attacks."