When I lived in Arizona (one of the places in the US with the most Lightning strikes per year) I did a voracious amount of hiking. Everything from deep sonoran desert hiking (meaning out in the open, little to no cover) to upper platte forest hiking along the Mogollon Rim. Every so often, especially in the summer monsoon months, I’d get caught in a decent thunder storm.
Being a New Englander by native decent, I was not used to having to find cover from storms. As in New England, one can find cover or shelter very quickly. So being out in the open during one of these large cell storms was an awesome sight to behold. There reaches a point in every electric storm where you can feel the electricity in the air. Almost sense that the air is alive. The atmosphere becomes almost a purply hue and the air get’s heavy, you just know the lightning is coming. I’ve been hiking several times when this happens and it is a scary time.
During an outward bound class, where we spent a week in the desert at the end of the semester (I was a 2nd year grad student at the time) we learned proper lightning safety. And in the desert, it was find the lowest point you can, and find it quick. Also, be aware of your bodies reaction to the storm. If you feel your hair start to rise, crouch down on the balls of your feet as quick as you can, because there is a streamer lifting from your body, to connect with the lightning’s energy, the connection would be the strike.
As we all know, lightning strikes from the ground up, the streamer goes from your body, the top of a tree, or a blade of grass to try and connect with the energy being emited from the storm, when the connection is made the strike happens. Many times people do not even know it, and if they are lucky enough to survive they wake up 20 feel from where they thought they were standing, dazed an confused, with a hell of a head ache and some burning…
To answer the OP, I’d find the lowest place I could and crouch down. The main part of being under a tree that is bad, is not being struck by the lightning, but by the shrapnal from the tree exploding next to you. I’d probably stay away from the trees. Unless you are in a forest, in which case I’d again, find the lowest place to ride out the storm…