The best months to visit Taroko Gorge are October to April. The weather is cooler and the skies clearer than in summer; from October to December in particular, Taiwan has its dry season and the gorge trails are in their best condition. The spring months (March-May) can be good but bring the beginning of rain; summer (June-September) is hot and humid with a significant typhoon risk.
Typhoons are the main practical concern: Taiwan sits in a typhoon-prone zone and a direct hit will close the entire park for days before and after the storm. The gorge road and several trails require inspection and repair after each major storm. Travel insurance and flexibility are advisable for summer visits. November is widely considered the optimal month: clear, cool, and without the summer crowds.
Weekends in summer attract large numbers of day-trippers from Hualien and beyond; the car park at the gorge entrance can fill completely by mid-morning. Weekdays, or any day before 8am, offer the gorge at its best.