Multiple lights coalescing and dispersing.

Weather conditions are hot and unusual for this time of year in MN, with a high in the 90's, conducive to storms.  Watching the weather front coming in around 7:00 pm - darkest to the east and south.
Between 7:15 pm and 8:00 pm, where the sky was the darkest to the south and east, I saw what I thought was a flock of birds behaving as a flock - coalescing, dispersing, going up into the clouds, then coming back again.  Many times they formed different designs, sometimes seeming symmetrical and rising beneath the clouds so some couldn't be seen.  I could see the undersides were round and bright white.  I believe there were at least 50 shapes I saw.  Unfortunately we could't get pictures.
After a while, realized what I was seeing was 1) too symmetrical to be birds and 2) too large to be birds.