There are no direct roads leading to Machu Picchu since the valley has space only for the tracks of this rail line. Fortunately, there are several train options: The luxurious Hiram Bingham train, connecting Cuzco to Machu Picchu, and the comfortable Inca Rail and Peru Rail options connecting the Sacred Valley to the Citadel. From the train station in Machu Picchu Pueblo, originally called Aguas Calientes for its hot springs, you then take a shuttle up to the ruins.
Peru is situated just South of the Equator, so the sun is very intense year round! But Lima and most of the coast is cooled by the Pacific Ocean, which is rather cold here. In the mountains around the Inca ruins, it is cool because of the altitude. Only in the Amazon and there only during the day you will experience tropical heat. There is no monsoon-like weather in Peru, like in Asia. In the summer (from December to March) you can experience heavy rains in the Andes and the Amazon. It never rains along the coast, which is a coastal desert. In June to August, it can get cold in the mountains, but it rarely rains there during that dry season. So just bring a good jacket along.