When I was in my teens, I lived in Wyoming, a state with a lot of space and not a lot of people. This provided some great opportunities for masturbating outside, and I used to take advantage of these opportunities every chance I got.
I vividly remember the day that I had planned to walk out to one of the wooded areas bordering the country club, where I knew of some paths through the woods (used primarily by groundskeepers, I think). Being a big fan of lubricated jacking, I was trying to determine how best to make it there with some kind of lube. I primarily used baby oil, but it's pretty hard to walk past a bunch of houses, around a golf course, and then make it into the woods with a lubed-up penis. I decided to revert to my original form of lubrication, a jar of petroleum jelly. I put a small jar into my jacket pocket and headed out for a walk. As I walked outside, I felt my excitement (and penis) growing as I breathed the fresh air and felt the warm spring sun on my shoulders.
Of course, it was hard not to run as I planned out what I would do; the urging in my groin was growing and pulsing with each successive step. By the time I made it near the edge of the wooded area I could barely contain myself. I was fortunate in that there were almost no homes near the edge of the golf course, as I began to strip off clothing almost the moment I made it to the edge of the woods. My jacket, my shirt, then my shoes, pants, and underpants. To be safe, I put my shoes back on, but was heading through the woods wearing only my sneakers and carrying my clothes balled under my arm. I hadn't yet got out any petroleum jelly, but my penis was stiff, throbbing, and swaying back and forth as I run-walked through the woods towards a little clearing where I planned to address my needs.
There were a place or two along the way where the woods weren't so thick, or where there was no cover at all apart from knee-high grass, but I went through and past it all in spite of the fact that anyone on the golf course could see what I would do. I made it to the open area in a copse of trees, set my clothes off to the side, and started smearing petroleum jelly all over my throbbing erection. I set the jar off with my clothes, with the plan that I would head into a deeper part of the woods if anyone came along and hope they didn't find my clothes. I then began jacking and pumping, slowly at first until the petroleum jelly warmed up, then faster and faster. Soon I was pumping furiously, wandering closer and closer to the path that led directly to the golf course. I got within about seven feet of the edge of the woods and was standing there in the warm bright sun, only somewhat surrounded by foliage until I noticed some golfers within about thirty feet. Of course, the excitement was too much and this just happened to be the instant my erection began squirting out the cum that had been building up for fifteen minutes. I stood there while hot white blob after blob shot, then squirted, then dribbled out onto the ground. I thought at least one of the golfers, a guy who appeared to be in his forties, looked in my direction just a little too long and figured I'd been seen, but he didn't appear to say anything to his companions.
I waited a minute or so until I was sure that I was done, then backed into the woods and began dressing. Too soon, I'd made it back home, but my memories of the day have lasted for decades now.