The time of the year can really make a big difference in the flow of water in the rivers. The flow of the rivers during the monsoon in July and August are ten times are more than the flow of water in March.

It is usually best for beginners to go on a trip after mid-October, when the rivers become milder. During the November the rivers are mainly fast-moving, but not too difficult. The busiest rafting season is in October and November. The best seasons for rafting are from September to December and March to early June. In December and January many river become cold and unless you have a wetsuit they may not be enjoyable. The winter is not as cold as might be expected because most of the trips are on rivers areas below 500m elevation. The rivers are the most mild between from December to April. During the winter is a slower time for tourism, there are less options with tour operator for rafting trips.

From March to the mid-May because the river flow is low, the rivers do not move as quickly. If the water is running faster on a river at a particular time of the year, the trip can take a shorter time than if it is running slower.

From early September to early October and late-May to late-June (when snow melts in the mountains and some pre-monsoon rainfall) the rivers can flow very quickly. During this time rafting can be more dangerous than normal. It is best to raft with an experience company at this time, because extra precautions need to be taken.
During the monsoon, from June to August only experts should do rafting trips. During this time there may be 10 times as much water flowing in the rivers. Rafting can only be done on certain rivers during this time.

Various rivers can be different depending on the time of year. Depending on the time of the year you are in Nepal, can adjust what river you go on.