Unless you are near the coast, Spain has a very dry and arrid climate. The nice thing is that it's never really that humid that you feel like you can't go outdoors, but it can get extremely hot, especially in the spring and summer. While the Spaniards are used to the heat, even they sometimes get overwhelmed by the temperatures. Temperatures can usually reach the high 90's- low 100's in the height of the spring and summer months. Granada can get extremely hot because it is in the deep south of Spain. Though it is located an hour from the beach and an hour from the mountains, neither the sea breeze nor the mountain chills reach the city. With that in mind, it is probably best to avoid visiting during the middle of the summer if you can avoid it or have problems with extreme heat. The best time to visit is probably in the earlier spring months or the fall. The reason for this is you will avoid the extreme heat, as well as the colder temperatures of winter. If you like to ski, however, winter is a good time to go because you can go to the mountains to ski, but it is not freezing like other locations where you would be skiing. Another thing to keep in mind is that Spain has tons of students studying abroad. During March, they will be on spring break and will be going wild all throughout the country. If you want to avoid this, plan your trip around that to avoid that mess.