Venus, as it turns out, was all we needed. 

It was uncertain how far west we were going to continue, but flickers of such bright light it had to be a plane (but no!), so low on the horizon warranted a quick reference to Sky Guide on my iPhone assuring us that it was indeed Venus, and not a plane, which meant clear skies were still ahead.

They didn't last forever, and it wasn't the entire sky, but it was very fortunately, perfectly timed.