High coolant pressure on 2015 Kawasaki Ninja 650 hot day

I live in Las Vegas, the other day on the way home from work it was about 100 degrees out. I got on the freeway and there was a big traffic jam. I spent between 20-30 minutes mostly idling and just inching forward.

I got home and shut off the motorcycle without thinking much about it. When I came out later to put it away there was a small but noticeable amount of coolant on the ground. And I could see spots where it shot down the right side of my motorcycle. I put it away, cleaned up the spill and then waited to see if anything else would leak. There were no new leaks, and I checked again this morning and there was still nothing new.

I have checked the hoses coming from the radiator and the radiator cap. Everything seems to be in working order. I need to make sure the coolant levels are fine, but I had three questions. One, would it have been spillage from the overflow tank? Two, is there anything else that you would recommend checking before I assume that the bike is ok to ride? Three, am I correct in that this was likely caused by the high heat + not being able to move and get air flowing? I think for the rest of the summer I’ll just take surface streets.

I’m reasonably handy with tools but I don’t know much about how the motorcycle cooling system works so this might be a case of the system working as intended given the circumstances.