Very good question! I’m glad you asked. I have a pink flowering almond Prunus glandulosa 'Rosea Plea' that has been flowering the last couple weeks.
Will be watching for others thoughts!
Plants booming in autumn is not all that unusual. Fall is the mirror of spring (temperatures and conditions can be similar for weeks). A drought in the summer can induce a temporary dormancy which ends as the cooler wetter autumn shows up...There are even cherry (prunus) varieties that are grown because they will bloom in autumn.