Is it normal when i love w/ gf that i feel much more horny outside than inside?

When I make love with my girl friend outside, like at a park or something, than just making out at my house. I feel so much hornier making love with her outside. When we're inside it's like the usual, undress and love. But outside, a field where no one is, a park bench, a place outside to make love. I get like twice as horny outside than inside. But my girl only will fuck if we're outside but not in public. I think when we make love where it's possible people can see us, such as outside, i get way hornier. It's just so kinky and thrilling when we feel each other on a picnic bench. I sorta feel like i'm violating public space, but at the same time it's so orgasmic. My girl even tells me i'm stiffer and warmer when we love outdoors. What's up with me. So, is it normal that when we make love outside vs. inside, that i feel more intense in love and hornier??