Nepal experiences five distinct seasons: spring, summer, monsoon, autumn, and winter. Because of the extreme variation in altitude, the Köppen climate classification shifts radically from tropical savanna in the southern Terai plains to subtropical in the mid-hills, and eventually to alpine tundra and ice cap climates in the high Himalayas.
The weather is heavily dictated by the South Asian monsoon, which brings torrential rains from June through August. During this period, the Terai and lower hills can experience severe flooding and landslides. Summers in the Terai are famously hot, often exceeding 35°C (95°F), while the Kathmandu Valley enjoys a more temperate summer averaging around 28°C (82°F). Winters are mild in the south and valleys, though nights can be chilly, while the high mountains experience sub-zero temperatures and heavy snowfall.
The best times to visit are autumn (October to November) and spring (March to May). Autumn offers clear skies, mild temperatures, and the best visibility for mountain viewing. Spring is slightly warmer and features blooming rhododendron forests, making it prime season for trekkers and mountaineers.