The best time to visit Bhutan is generally considered to be during the spring (March to May) and autumn (September to November) seasons.

Spring (March to May):

• Pleasant weather: The weather is mild and dry, with clear skies and comfortable temperatures.
• Blooming flowers: The valleys come alive with colorful rhododendrons, wildflowers, and other blossoms.
• Trekking: It's a great time for trekking, with trails open and the weather ideal for hiking.

Autumn (September to November):

• Clear skies: Autumn offers the clearest skies of the year, providing stunning views of the Himalayas.
• Dry weather: The weather is dry and sunny, making it perfect for outdoor activities.
• Festivals: Several major festivals take place in autumn, offering a chance to experience Bhutanese culture.

Other factors to consider:

• Winter (December to February): While it can be cold, winter offers fewer crowds and unique experiences like seeing black-necked cranes.
• Monsoon season (June to August): The monsoon season brings rain, which can disrupt travel plans, but it also means fewer tourists and lush green landscapes.

Ultimately, the best time to visit Bhutan depends on your preferences and what you want to experience. If you're looking for pleasant weather and outdoor activities, spring and autumn are ideal. If you want to avoid crowds or see specific events, you might consider other times of the year.