It is really hard to say in KM but, About 900 KM will be traveled from Kathmandu to reach Rara Lake. About six Hundred KM  (15/16 Hours) to reach Surkhet & About 180 km travel to reach Kalikot Manma & about 100/120 to reach Rara Lake but almost all the road is offroad. 

There is no direct flight from Kathmandu to Rara Lake; instead, you must fly to Nepalgunj and then to 

Jumla or Talcha from Nepalgunj.

PLANE TRAVEL: 

(Flights range from $150 to $200.)

1. Nepalgunj (60 minutes) from Kathmandu or Pokhara

2. Nepalgunj to Talcha [35 minutes] (closest airport to Gamghadi, where the five-hour journey to the lake begins)

3. It takes around 35 minutes to walk from Nepalgunj to Jumla (a four-day walk to Rara Lake).

TO RARA BY BUS: (Bus tickets vary based on where to and how many buses you will need)

1. NEPALGUNJ to Kathmandu: $12 USD [Around 8-10 hours]

2. POKHARA to NEPALGUNJ: The journey takes between 15 and 18 hours.) - 12 dollars

3. NEPALGUNJ to GAMGHADI: (no buses available; best bet is to fly; but, if you ask around upon arriving, you might be able to get a shared jeep)

4. NEPALGUNJ to JUMLA (may be done in a shared jeep for 2000 NPR/18 USD and takes 9-12 hours)

Buses run, although fares and services are unknown; inquiries can be made at the Nepalgunj Airport.

Instead of flying, Jeeps are frequently chartered from Nepalgunj to drive the rest of the way.

The trek to Rara Lake might take four days to more than two weeks. While the walk is not particularly long, travelling to and from the starting and conclusion places can be time-consuming.

No. There are guides available for those who want them; you may hire a guide who will start from Jumla, or you can discover several firms who will put together your schedule from Kathmandu and take care of all the flight arrangements.

The Rara Lake Trek is not challenging or lengthy, and it is suitable for trekkers of all levels. It does, however, necessitate a basic level of fitness. This is an attractive option if you have no previous trekking experience. There are many other trails to challenge yourself and enhance the experience for those who want more of a challenge and have the time.

1. September and October: The cool, breezy temperature and lovely misty views are ideal for these Spring months. At the end of October and the start of November, It is warm & the weather is pleasant.
2. April and May: These are the summer months, when the weather is clear and sunny, making trekking more predictable.

March is also an excellent time to visit, as the weather will be mild, and the Himalayan views reflected in the lake will be beautiful during any of these three summer months. If you arrive during the rhododendron season, you'll be especially luckier.

Although the villages specified on the route, there are few tourist amenities will have tea houses with very modest rooms and meals - dal that is always a good bet; the hotels near the lake offer some excellent fries and masala chai. Showers and restrooms are in short supply, so plan appropriately.

There are possibly 20 animal species and 214 bird species to observe, including the common Danfe pheasant, Nepal's national bird, and over 500 flower and herb species.
Lake Rara is home to otters, fish, and ducks. The clouded leopard, ghoral, rare red panda, serow, musk deer, and Himalayan black bears may all be found in the National Park's blue pine, oak and cypress, black juniper, and rhododendron woodland.
It's also home to over 200 different bird and butterfly species. During the winter months, migratory birds from all over the world may be seen, while during the summer months, Himalayan flowers surround the lake, creating a vivid environment.