September marks the end of the monsoons in Nepal. However it still rains quite a lot in September.
It generally rains around 168 mm (about 6 inches).
There is a possibility of rain for about 12 days throughout the month.
The average daily temperatures are around 23°C (73°F), reaching highs of 26°C (79°F) and drpping to an average minimum temperature of 19°C (66°F).
It is still quite quiet during this month due to the rainy and cloudy conditions.
However tourist and trekking enthusiasts start arriving in Kathmandu from the end of September.
The end of the hot and humid weather with torrential downpours means that once again hiking on the mountains is possible and the natural beauty that Kathmandu is renowned for is once gain more visible.
September is a great time fo year to visit should an active, hiking holiday be what you are looking for.