If someone could predict when airlines will offer the best/lowest fares to any destination they could make a fortune selling that information to travelers all over the world. Unfortunately no one can predict when or if airline's will have a sale. All the can do is tell you fares will fluctuate.

Your best bet is to monitor fares for your planned dates of travel to get an idea of the "fare range. then, when you see what looks like a good fare don't hesitate book your flight. That "low fare" may not be there the next day (or even an hour later).

Hint - sign up for airfare email alerts with your airline(s) of choice and on travel sites like kayak.