I could do with one or two nights of 30 to 31 deg (F) weather (0 to -1 deg C). It rarely freezes in the East Bay, but believe me: when it does, the next spring's **flea** season is much less intense. With black long-haired dogs and multiple cats, this is a Big Thing for me personally.
My plants in the ground right now are cold-hardy veggies; my cymbidiums are hardy to 28 deg F. Yep, they've been tested. I even had them out one year when it went down to 23 or so, but they were under the carport roof. Lost some major jade-plant trunks that year, though, but not entire plants. *whew*
It could still happen; we've occasionally had February freezes, but usually when they've happened, they've been in late December or sometime in January. sigh...
Sunset Zone 17, USDA Zone 9