I live in the panhandle of Florida. At times it can dip into the mid or even low 20s for short periods of time. I am looking to get the biggest clumping bamboo that will safely grow in my climate.
Bambusa distegia, bambusa malingensis, bambusa dolichoclada and variations, bambusa dolichomerithalla and variations, Bambusa eutuldoides 'Viridivittata' - Asian Lemon Bamboo and Asian Lime, Bambusa Beecheyana (some species not infected with the mosaic potex virus), Bambusa Chungii, Bambusa Dissimilis, Bambusa Textillis Kanapaha, my personal favorite Bambusa Ventricosa 'Clone x', Bambusa Ventricosa, Bambusa Dissimilator Bambusa eutuldoides 'Basistriata'. These bamboos are all clumping and have a cold tolerance of 21 or lower. While their cane thickness is 2-3 inches depending on species. However a few would not be considered "timber bamboo". Are you using the bamboo as a hedge/wall, specimen, or crafts?
The largest clumper here, with similar temps as you, is Bambusa textilis, growing to over 40 feet in height and a very neat looking bamboo. It is the cold hardiest of the large clumpers for this area and rarely gets any damage, even with temps down into the low teens for short periods.
Bambusa oldhamii grows to similar height, has larger culms, is more erect/upright but is not quite as cold hardy so it might need some northwind protection.
I have others that get large, but get burn by cold weather and sometimes the culms even freeze back.