Mine started turning 2 weeks ago here in the pacofic northwest.... when the nights started to dip to low 60s high 50s (58-59) the San Marzanos began to ripen.
I think it is related.
This is my 1st time geowing them. My heirlooms have been ripening previous to the cool night time temps...in the 70s.
The local garden show said to take a shovel to them, cut the roots 6” or so from the vines to stress ‘em, failing that dig ‘em up shake the dirt off the roots and hang them upside down in the garage.
I think I’ll give it a couple weeks of cooler weather before I do anything like that!