Autumn: September to November
Excellent season for trekking in all areas, clear mountain views.
Winter: December to February
Ideal for trekking in regions below 2500 meters altitude.
Spring: March to May
Nepal's national flower Guranse (rhododendrons in English) colors the mountains, moderate temperature makes a perfect choice for trekking in hilly regions but trekking in terai can be a little burdensome due to high temperature in the region.
Summer: June to August
Monsoon is in the period. Expect wet, warm and wild trekking during the season. This is the season to see lush green valleys with rice crops and greenest thick jungles.