Approaching 100% there was a developing twilight, but it did not seem like a evening twilight because the colors did not turn red and shadows were at the wrong angle. The light took on a gray cast. At the instant it reached 100%, there was a sudden darkening, a few stars were visible, but it was not a nighttime dark. Lots of ambient light sensors were confused. Things can't appear absolutely dark because the shadow of totality is basically a point at ground level, while some light diffuses in from side areas that are still fully lit. Another aspect is that our vision system is not equipped for instant darkness accommodation. Depending on your exact location, there could have been some fully illuminated nearby clouds. One nearby observer remarked that, as totally approached, his camera case was not as hot as it had been earlier. I didn't measure any temperatures, but it seemed much cooler because less light reached my body.

Great show! If you missed this one, although it will not be quite as spectacular, the next big show will be in 2024 -- start checking the long range weather forecast, pick your location, and make reservations now.

Edit: There is a certain amount of "the luck of the draw" with respect to weather. And, this can vary almost block by block. At my viewing location the history of cloud cover was not grand, but I took the risk -- and it paid off handsomely. The location was nearly cloud free. During the early stages of the eclipse there were a few wispy clouds passing rapidly over the sun, but they were small and not very disruptive. Afterward, I spoke to an individual observing from a few miles away and a passing cloud blocked his view of totality.