I don’t remember these in Utah but where I live in Southern California they are everywhere. They are the western spotted orbweaver. They aren’t aggressive or dangerous. They are venomous but supposedly it is really mild. I’ve never even heard of anyone ever being bitten by one but they are crazy good at making webs.
These spiders will create webs 10 feet across in a handful of hours, usually overnight. It is common for me to get up early in the morning to walk the dog down the trail next to my house and walk face-first into one of their spider webs spanning trees on either side of the trail. That is immediately followed by my flailing around to get all the spider web off me and violently brush my clothing to make sure no spiders are on me. For some reason my dog never clears the webs before I walk into them because these spiders prefer to spin webs at human face height.
