Last year and this year, we had very cold lows that occurred while many deciduous trees & shrubs were still carrying green leaves. This interrupted the normal process of gradual winter onset where the leaves cycle through green to reds & yellows, and then drop off the plants two years in a row. What your left with are so many trees where the leaves are basically freeze-dried on the stems & branches. It's unsightly, but one wonders if it's also damaging beyond the visual appeal of the trees.
Last year, the cold shot happened on November 11th. The mercury fell to 20F. The species most starkly affected were Japanese Maples. This year, the cold came a little later, on the 22nd and 23rd, with temperatures of 20F and 16F. The big loser this time seems to be Bradford Pears. The leaves on many of these trees are now black!
Most of our Zone 7 landscape trees can take temperatures in autumn, after hardening off, down to 25 or 26F without much damage to living leaves. But they don't take 20F, much less 16F.
Two years in a row. Makes you wonder if anything's going on.