The best time to visit Itanagar is October to April, when the weather is dry and clear. Winters (November to February) are mild in the city itself, though cold at higher altitudes, and the air is sharp and clean. Spring brings rhododendrons into bloom across the surrounding hills.
Avoid the monsoon months from June to September. Arunachal Pradesh receives heavy rainfall — some of the highest in India — and landslides frequently close roads. The approach from Assam can become impassable for days at a time. If you must travel during monsoon, allow plenty of extra time and check road conditions before setting out.