"The dates of the World Cup will not be in June or July. I think it will be played between November 15 and January 15 the latest," he told France Inter Radio.
"If you play between November 15 and, let's say, the end of December, it's the time when the weather is the most favourable," Valcke added.
"You play with a temperature equivalent to that of a rather hot spring in Europe, you play with a temperature of 25 degrees (Celsius), which is perfect to play football."
In October, FIFA delayed making a decision on whether to play the tournament in the winter saying it was setting up a consultation process to decide when the finals should be held.
At the time, soccer's world governing body announced it would reach a conclusion sometime after this year's World Cup in Brazil.
Valcke's surprise announcement on Wednesday comes more than three years after Qatar was originally awarded the tournament in December 2010.
The average temperature in the summer months in Qatar can be around 35C (95 Fahrenheit) and 45C (113F).
(Writing by Mike Collett in London, additional reporting by Julien Pretot, editing by Ken Ferris)
