Winter in Nepal sees high pressure weather dominating, so the weather in February is settled and dry. Daytime temperatures can be pleasantly warm, particularly as the month draws on, so it's a good time of year for sightseeing. Temperatures drop quickly once the sun goes down though, so you need warm clothing for evenings and early mornings.
February is low season in Nepal with fewer visitors, but spring is on the way and the temperatures are slowly picking up, especially across the south and centre of the country. Days are typically clear and bright and it's not too hot, with temperatures in Pokhara and Kathmandu a pleasant 20°C. The narrow streets and buzzing markets of Kathmandu will be more manageable in the comfortable temperatures and prices for accommodation tend to be very reasonable.
At high altitude there's often snow. Lakes are frozen over, flights to places like Lukla can be disrupted and sometimes high level lodges get snowed in. Teahouse trekking on lower level trails is still perfectly practicable, but you need to be well insulated against the cold. Daytime temperatures are typically around 5°C with minus temperatures expected during the night. It's a good time of year to explore the flat plains of the Terai region that runs down the border with India and includes Chitwan National Park, the holy city of Janakpur and the Koshi Tappu Reserve with its excellent bird watching.
Taking an alternative approach to a classic Nepal combination, this journey contrasts the heady and hectic streets of Kathmandu with the open savannah of Chitwan National Park. Slow down to search for tigers and rhinos amid the wilderness, before strapping up your boots for a light trek between two atmospheric lodges in the Himalayan foothills around Pokhara.