How cold hardy are Rhode Island Reds?

[Willowbird45]

I am on the fence about what to do - I keep reading that chickens will do fine in cold - howver, I had one die last night, for no apparent reason. It was in the mid 20's (SC) and I found it dead in the middle of the run. I have a 12x5x8 run attached to a 5x5x5 main coop with 6 nesting boxes hanging off the sides. I only have 7 birds, now 6. 3 were slightly younger - and they had their own small coop box inside the run - and that is where those 3 slept as well.....they won't sleep in the big coop - but lay there. So, tonight - I shoo'd the other remaining 2 younger ones - into the big coop. I was planning on turning on a heat lamp - but now after reading this - that seems stupid - if they are fine below zero.....surely they should be okay in mine. That is what I am told, and read - but yet one died last night - and none of them looked sick at all yesterday. None of my birds have every been sick - I've had 4 since last May 2020....got them at 4 weeks. Then 2 months later, I got 3 day old chicks. So they are all laying age now - and were laying. I think I will not turn on the lamp. I hope the 2 younger birds do not get tortured in the big coop tonight.