The governing body's executive committee is due to discuss the move in October, and Blatter remains confident that his colleagues will side with him on the matter.
"We still have enough time," BBC Sport quotes him as saying. "The executive committee will certainly follow my proposal. Then we will have dealt with the topic for good.
"The World Cup must be a festival of the people. But for it to be such a festival, you can't play football in the summer.
"You can cool down the stadiums but you can't cool down the whole country and you can't simply cool down the ambience of a World Cup. The players must be able to play in the best conditions to play a good World Cup."
Matches at the 2022 World Cup will be played in air-conditioned stadiums, but temperatures in Qatar can hit up to 50C.
Qatar's organising committee is believed to be open to the possibility of a winter World Cup should FIFA rule that a seasonal switch is necessary.