You don't burn tracks so much as you delaminate them (or maybe burn them, I dunno). But you'd probably want to keep the temperature below 60C. When a component is rated up to "85C" that does not mean it can operate when the ambient temperature is 85C. It means that the maximum temperature rise plus the ambient temperature can't exceed 85C. Your ambient is probably not going to go above 35C unless it's next a car engine, in direct sunlight, in a greenhouse effect type area, or a desert, or something like that.
If your ambient actually is 85C well most components aren't going to work anyways since they're already at their maximum temperature even when they dissipate no power. Suppose that wasn't a problem, FR-4 has a maximum temperature of 120-140C. Let's say 120C just to be safe, and probably even more since you don't want to be anywhere near that temperature (and much more if any heat transfer along the board pushes other components past their maximum temperature). You're trying to hold off a 35C temperature at most which is typical for many power components. Large traces, no way around that.
But your ambient probably isn't that high anyways so you're probably fine.