The months of October and November happen to be the best months for visiting Kathmandu.
The weather and visibility during this month are just perfect for trekking and outdoor activities.
The average daytime temperatures are around 20°C (68°F): just the perfect temperature to enjoy hikes and walks around the town without getting sweaty.
However it is advisable to carry some warm and light jackets as the evenings can get very chilly.
October has also got fair chance of rain, however if it does rain it does not last for more than a couple of hours and is usually followed by clear weather.
The other important thing to keep in mind is that there is a huge shortage of electricity in Kathmandu and that the electricity board carries out load shedding throughout the day.
Most parts do not have electricity for 5 to 8 hours.
However most of the big hotels have backup generators; it will be convenient and less stressful if you make sure that your hotel has got one.
If you are not able to find accomodation that boasts a back up generator, make sure you take advantage of the electricity whilst you do have it, and charge any phones or cameras you may have on you that you will be needing.
This will be far more convenient for you.