Each season, whether it is spring, summer, fall or winter, can be a peak or an off-peak season depending on where you want to fly. Cooler areas such as Europe, Canada, Alaska, the Pacific Northwest, and Maine and New Hampshire are popular destinations in the summer. The Caribbean, however, is cheaper in the summer than in the winter, as people avoid the higher summer temperatures. Ski locations such as Aspen are popular destinations in the winter but not in the summer. Fall is leaf-peeping season in New England, Canada and other places that have fall foliage, and prices rise accordingly.
Popular holidays such as Christmas and Thanksgiving create high demand for travel and airlines raise prices accordingly. Spring break is also a popular time for students to travel to places like Florida, Mexico, Las Vegas and the Caribbean. Keep holidays in mind to figure out if a travel time is peak or non-peak. Blackout dates on fares provide clues as to what the airlines consider peak times.
Alaska, with its mild temperatures in the summer, is a popular destination for tourists, but less popular in the winter, making winter its off-season. Likewise, the Caribbean, with threats of hurricanes in the summer and fall, is a less desirable destination in the summer, making that its off-peak season. Contact the airline you are thinking of using to find out their peak and off-peak dates for different destinations.