Blatter said FIFA officials and others "are starting now the consultations" on whether to move the World Cup from its traditional June-July slot, a decision that could drag into 2015.
"And when I say winter, I mean it can only be November and December," he told reporters in Abu Dhabi before the final of the Under-17 World Cup. "It can no way be January or February."
Blatter, an IOC member, opposes the first two months of the year because it would clash with the 2022 Winter Olympics. He has suggested kicking off the tournament in November.
An April-May option has been proposed by Karl-Heinz Rummenigge, chairman of the influential European Club Association which will be consulted by FIFA. Qatar hosted the Under-20 World Cup for FIFA in April 1995.
January is favoured by UEFA President Michel Platini, potentially Blatter's rival in the next FIFA leadership election in 2015.
Blatter is scheduled to travel to Qatar for the latest round of discussions on whether to hold the tournament outside the Gulf summer, when temperatures can reach 50 degrees C (122 F). A FIFA panel is studying the move, but organizers in Qatar claim their plans for air-conditioned stadiums and other cooling measures could allow them to fulfil the hosting promises made when bidding.
Blatter will also discuss labour issues with the Emir in Qatar, and is then scheduled to hold a news conference on Saturday afternoon in Doha.
Like other Gulf states, Qatar relies on migrant workers mostly from South Asia. Rights groups have long complained about abuses across the Gulf such as substandard living conditions and employers holding workers' passports.