Anything 15C or higher. If that's the high for the day and the sun is barely out, I MIGHT put jeans. Depends what I'm doing. In the sun it's still pretty hot especially if doing any kind of physical activity.
Anything below that is jacket weather. If I'm not going to be outside for long I might get away with just a tshirt but otherwise at least a windbreaker. And yall and your friggen commie temp system.
I kid I kid, I know metric and Celsius are far superior and we are just idiots that won't let it go.
