I too use to love studying outdoors the most. But, at my college, there is so many things that end up getting into my backpack if I just spend an hour under a tree. I end up having these bugs that I have never seen before make their way up my pants and into my hair. Though, they seem harmless, it still "bugs" me. However, during the colder months, the insects start to die down and I just love the solitude.
I can't really say there is one place... I get bored with only one place, so I tend to walk around a lot. I like studying in the coffee shop, especially with a study group.
When it is rainy or too cold/hot outside, I end up stuck in the library, which really isn't bad at all. This is probably the most effective way to study if you get distracted easy like me. hahaha. It is so quite and you can really focus.