Every destination has an ideal season, but what is best for you depends on what you want: mild weather, lower prices, or a seasonal experience such as cherry blossoms.
Start by choosing your priority: the best possible weather even if prices are higher, or good weather with lower prices and fewer crowds. The shoulder seasons between summer and winter (spring and autumn in most European cities) often give you both.
Watch school holidays and local festivals at your destination; they can raise prices and crowds even in good months.
Remember that seasons are reversed in the southern hemisphere, so the best time to visit Sydney or Cape Town differs from London or Paris.
Use the Seasonal Rhythm section on our homepage to compare the months of the year for several destinations before you decide.