There are a large number of sugar maples planted in and around Columbia, MD where I live. Many are street trees (not the best street tree, but I digress).

There is an interesting thing that happens to them, that I am noticing just getting started this year.

They leaf out normally, a nice dark green that A. saccharums are known for. Then, around mid-June, parts of the tree (rarely the whole tree, usually a single side or upper quarter) starts yellowing a bit. Not true yellow, but turning a lighter green. One tree even had some orange in the leaves as if it were fall. That tree in particular I remember that side of the tree turned autumn colors VERY early last year, while the rest of the tree waited until late October.

The specimens most prone to this seem to be along streets, near pavement. The occasional sugar maple farther back off the road with "room to move" and grass/dirt/mulch under its entire dripline, these mostly look just fine.

Is this typical stress from pavement/compacted soils/etc? Other trees do this too but Sugar Maples seem the most prone around here. I don't think it's heat stress (hasn't been that hot) but it could be TOO MUCH water, as we have clay soils and the first 2 weeks of June we had 6" of rain. Most trees are the 'Green Mountain' cultivar, I think.