Is it normal to get a boner in the rain

It was a stormy summer afternoon. Actually, it was more than stormy; it was raining cats and dogs. Branches were coming down, the wind was whipping, and the storm drains were overflowing. After a humid day, I threw on my swim trunks and ran out into the storm. After a couple of minutes of roaming around my college campus in the rain, I spot her: my girlfriend's roommate.

My girlfriend and I have been together for nearly two years––things are really good. This girl I spot from afar in the rain was her roommate freshmen year. They didn't exactly get along great, but for all my self-restraint I couldn't help but ogle at her roommate. She was a novelty on our campus. A small girl of African descent with deep chocolate skin and the most adorable (and naive) personality. Here's the kicker though; she has an enormous set of tits. Larger than a DDs, they wouldn't fit properly in any top she wore, no matter how hard she tried. Whenever you met her in the hallway or the cafeteria, you would hopeless try to carry out a friendly conversation while gaping at an avalanche of cleavage squeezed into a tank-top. And this isn't just my opinion; she was well-renowned for having some of the best boobs around.

In this scenario, I saw her, let's call her Chalise, walk around the corner of a building as I was admiring a fallen branch in the rain. My heart nearly gave out when I saw who it was. As the only other soul in the thunderstorm, she headed in my direction. As she neared, I realized she was in a loose white dress shirt that was now drenched. Everything was on easy display; bra, cleavage, belly button, you name it. Now typically I would only exchange pleasantries with Chalise, in attempt to avoid any sudden urges. However, in this scenario my manhood immediately took control and started engaging her in a thorough conversation.

So there I was in only my swim trunks, talking to my secret fantasy in a wet t-shirt (seemingly unbeknownst to her) in the rain. I stalled, taking in as much of her chest as I could, regardless of whether she was looking at me or not. We talked about the storm, our summers, classes, and about who's she was out looking for in the rain. And the whole time this was happening, I could slowly but surely feel a tent begin to rise in my trunks. I tried to think rationally and will it away, but I couldn't––and almost didn't want to––stop it. By the end of our five minute conversation I certainly thought I was at full mast and I saw her eyes flash once or twice towards my legs. We exchanged goodbyes and she walked back off around the corner. After the delayed wave of adrenaline and awe, I instinctively looked down to see my hard cock outlined at full length alongside one side of my wet swim trunks. Despite my subconscious attempt to stagger my stance in a way that would make the tent in my trunks blend in with my knee, it was obvious I had a massive boner.

We have never spoken of it since. Did I do anything wrong? Is this a minor form of cheating? Is it possible she didn't notice? Any comments or advice would be helpful.