Sun Moon Lake is beautiful at almost any time of year, but conditions vary considerably. Autumn (September–November) is the most celebrated season: clear skies, comfortable temperatures, and the annual Thao harvest festival and swimming competition held in late September or October. Spring (March–May) is also good — the tea on the surrounding hills is harvested and the mornings are cool and clear.
Summer (June–August) brings heat, crowds, and the possibility of typhoons; the lake can be dramatic in stormy weather but access roads sometimes close. Winter is mild and much quieter, and the mist on the water is particularly atmospheric — you may have the cycling path largely to yourself on a weekday in January.
The most-visited period is the mid-autumn festival and the surrounding weeks, when Taiwanese domestic tourism peaks.