Nepals climate is influenced by maritime and continental factors, and has four distinct seasons. Spring lasts from March to May, and is warm with rain showers and temperatures around 22°C. Summer, from June to August, is the monsoon season when the hills turn lush and green. Temperatures can get quite warm, up to 30°C and more during heat waves. During this season, trekking in most of Nepal is difficult and uncomfortable, the trails being very muddy. Autumn, from September to November, is cool with clear skies and is the most popular season for trekking. Temperatures are not too warm, with daily maxima about 25°C and cool nights with minima of 10°C, it usually does not rain for more that one or two days during the entire autumn and the winter season. In winter, from December to February, it is cold at night with temperatures sometimes below zero. However, the maximum temperatures can still reach up to 20°C. Then the mountains are covered with snow including some high hills.

The climate varies considerably with elevation. May to October is monsoon season, when rain soaks the Terai and snow falls on the Himalayan peaks. Mid-October to mid-December is prime mountaineering weather: the skies are clear and sunny, temperatures range from warm in the lowlands to crisp in the mountains. March and April are also good months for mountain treks, although temperatures in Kathmandu and the Terai tend to be steamy.Nepal has two seasons - the dry season from October to May and the rainy, monsoon season from June to September. Early spring (March to April) and late autumn (October and November) are the best times to visit, and also offer the clearest mountain views and good weather for trekking. From December to February there is snow on the mountains with freezing temperatures at high altitudes, while the summer months of June to August can be very hot for general travel.

Kathmandu Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Rainfall (mm) 25 25 75 50 100 225 375 360 175 50 10 10
Rainfall (inches) 0.9 0.9 2.9 1.9 3.9 8.8 14.7 14.1 6.8 1.9 0.3 0.3
Avg Temp (°C) 8 11 16 20 22 23 23 23 22 18 14 10
Avg Temp (°F) 48 53 61 68 73 74 74 74 72 66 58 51

The climate of Nepal varies from warm summers with mild winters in the low-lying southern region, to alpine conditions with very severe winters in the mountains. Between December and February temperatures drop well below freezing in the mountains. The best time to travel to Nepal for trekking is in early spring or late autumn, when the weather is dry and temperatures mild. The monsoon season on the coast occurs between June and September.