Sudden flash lights up evening sky above cornfields in rural Manitoba

Sudden flash lights up evening sky above cornfield just outside Belmont, Manitoba.  I was alone at home at the time and was startled by the entire sky lighting up super bright for a split second and then going back to normal.  This was a while back so I can't remember if this was the case exactly but I think I recall a boom-whoosh kind of sound that occurred at the same time of the flash.  It wasn't lightning because there wasn't a cloud in the sky.  All the power had gone out for about ten minutes before coming back on.  I talked to my neighbors a mile down the road and they said their power also had gone out but they don't recall a flash.