It is actually rather cool throughout the year. Last time that I visited Doi Inthanon was in January which is the coldest month of the year. I was really happy to visit there as the weather was very fine for me.
Apart from the weather, there are a lot of majestic and magnificent waterfalls that you can pay a visit and take some relaxation. Among those waterfalls are :
) Mae Klang Waterfall
It is the first waterfall that you can see on the road to Doi Inthanon as it is located at the foot of the mountain. It is the largest waterfall which is very beautiful and impressive.
) Mae Ya Waterfall
It is considered to be the highest waterfall in Thailand. Many travelers love to take tons of photos due to the beautiful widening series of steps. (drop meters in cascade form)
) Vachiratharn Waterfall
It is halfway up to Doi Inthanon so it is a good break to visit there for some relaxation. It is a nice waterfall for you and your family. It is very beautiful. It is very amazing that you can get wet when you go closer to the waterfall as the water runs fast from the top.
Apart from waterfalls, there are some lovely gardens with beautiful cold-climate flowers. I can say that they are all incredible flowers indeed. They are also great places to see various attractive plants as well. Those beautiful plants are covered in very pretty flowers. The places are full of drama and color at the moment you arrive! They are ones of the remarkable places that you won't miss!
Moreover, if you are a bird-watching lover, Doi Inthanon is highly recommended for you as it is considered to be one of the best place in Thailand for bird-watching. There are various kinds of birds making their home in Doi Inthanon National Park.
Furthermore, there are many hill-tribes such as Karen, Hmong, etc. You can visit their villages to take some beautiful photos and buy some fantastic products that were handed made by those hill-tribes. Especially if you are a textile lover, you will find some nice souvenirs of traditional Karen weaving and textile at the Karen weaving village; i.e. Ban Pha Mon, Ban Mae Ab Nai, etc. And the Hmong's embroidered clothing are very colorful as well.
As you can see, those are the main reasons why Doi Inthanon is a popular destination of Thailand. You are highly invited to see those beautiful scenery by yourself. Have a happy and wonderful traveling!