Heat lamp necessary for grown hens on 15 degree (f) night?

We have 25 hens that sleep in a closed-in, but somewhat drafty henhouse in North Carolina. We’ve had nights in the low 20s, but more regularly in the upper 20s. The hens have been very hardy in the cold, with little to no drop in egg production, and no signs of other cold-related issues. Tonight it is supposed to get unusually cold—into the mid teens. Do I need to run a heat lamp out to the hen house? We have rhode island reds, golden comets, and auracanas—all full grown. I have some concerns about predation but am not sure if the light would even attract attention here in the country. I assume most animals will be burrowed in for the chill anyway. (sorry, i’m not sure why that text above has a line through it).