Pretty much any time I am out among people, or driving in anything but light traffic, I am overstimulated. I had built up some resistance to it when I had to work for a living. Now that I am retired and not regularly exposed to the mayhem, I find I have less resistance to it - in other words, it now takes less to overwhelm me. At least I have my woods to retreat to.
I resonate with this very much.
It feels like the outside urban world, as well as any place with someone else than me in it, is
overstimulating all the time. That doesn't mean that I get
overstimulated or
overwhelmed all the time. It does feel like a constant knocking on my brain. Sometimes I'm relaxed and well, and then it's easier to tune it out and to not get overstimulated. Other times, I'm tired/over-/underheated/hungry/stressed/need to go to the bathroom/ill/in a busy place, and things will get overwhelming.
I had a phase of, let's say, about half a year around the end of my studies where I believe that I was either burned out, or getting dangerously close to it. During it, I had almost daily meltdowns with crying, snapping at everyone, and a strong need for isolation from any stimuli, specifically social, noise and visual. During that time, I was overstimulated on most days, and often all day, it was just a question of how badly.
By now, I'm overstimulated daily, e.g. on my way to and from work at train stations and in public transport, but I usually manage to not get overwhelmed. I don't believe it's possible to go outside and not get overstimulated at all. On otherwise good days, I don't really mind it - it's a lot, but it also enables me to see and take delight in things around me that others seem to ignore: birds flying, sun streaks on the sky, the sky's shade of blue, how a breeze feels, a patch of flowers. Getting all the extra input feels tiring, but on good days, I can take it and keep my brain controlled by listening to music. On worse days, it adds up and becomes overwhelming.