Five small triangular craft hovering then moving slowly above Ceres, CA.

While walking south on Richland Ave toward Hatch Rd, I observed 5 small objects hovering motionless over the downtown area of Ceres, CA.  This would be approximately south of me bordering US 99.  They remained in this position for approximately 10 minutes.
As I neared Hatch Road the objects began to move toward me and were directly overhead just before I reached the intersection.  A young male and female in a car pulled over and the young man got out and asked me what they were.  We watched them for a few minutes as they continued north and out of sight.
My estimation of their speed was 15 mph and the height was about 100 feet.  They were flying in formation and I could hear no noise from them until they were directly overhead when I could hear an extremely faint whooshing sound.  The objects were small, perhaps the size of a hang glider and triangular in shape.  They each had a small white spotlight on the lead corner shining straight out like a headlight.
A few minutes later when I reached home I called the tower at the Modesto airport to see if they had observed these craft as it was only a short distance away.  They reported not seeing it.
Witness indicates that the date of the event is approximate.  PD