What is the weather like in Nepal? What clothing should I bring along to wear?

It depends on where you are in Nepal. Generally speaking you should bring winter clothing/more layers in the months between November and February, and light summer clothing the rest of the year. May and June are the hottest time of the year. If you are planning to visit Nepal between June and September you should bring a waterproof jacket, as this is the rainy season. The temperature in the daytime can rise to between 30-40C in the summer and in the winter it can still reach 20C - but can be near freezing at night. Although you shouldn’t be too concerned if you don’t get it quite right because you can buy almost anything relatively cheaply in Kathmandu.
It is also important to respect local tradition & sensitivities - it is therefore not appropriate for women to wear short skirts or shorts, skimpy tops or clothing that is considered too revealing. For women it is best to have your shoulders covered and skirts/trouser till below the knee. For men t-shirts/shirts at all times, as being bare-chested is not deemed appropriate, nor are skimpy shorts. Shorts just above knee are fine, although in general for your own comfort and safety longer pants (e.g. lightweight trekking trousers) are most suitable. In rural areas good footwear is essential for safety given the often-rugged terrain.