The delicate pink flowers of redbud trees are often an indication of the first signs of spring, not autumn. The main reason a redbud would rebloom this late in the season is in response to stress. As a defense mechanism, a tree might rebloom in order to set seed. This could be a sign of overall decline and is a natural safeguard, in case the tree does not have reserves to come out of winter dormancy.
It is blooming early enough that if the stressors can be addressed in time, new shoots should have time to harden-off before frost. However, extra care is required. Check into possible stressors; nutrition, poor drainage issues, insect borers, persistent disease issues, voles, etc. and treat as needed.
In the case of this redbud, Cercospora leaf spot was a contributing problem. While generally not a big issue, it can cause early defoliation and is more prevalent in stressed trees. Cultural practices like cleaning up fallen leaves, pruning and discarding dead wood will remove excess fungal spores from the site. Red bud is a short-lived (<30 yrs), understory tree, that prefers good drainage and regular watering. A 2” layer of mulch out to the drip line can help with moisture retention. A soil sample (boxes available an your county Cooperative Extension office) can provide lime and fertilizer recommendations to eliminate pH or nutrient deficiencies as a stress factor.
If you have a landscape horticulture problem but are not sure what kind of signs to look for, contact Anson Extension Agent Aimee Colf at 704-694-2415 or aimee_colf@ncsu.edu.