My 5s used to shut down if it was exposed to the elements and the temp dropped below about 27F. My 6s shuts down below 40F?

I mount my phone on my bike, in a protective case. I learned from experience with my 5s that this was OK until temps dropped a bit below 30F. My 6s shuts down below 40F. When I try to restart it, I get the dead battery image. After I warm it up for awhile, battery restores to its actual status and the phone is fine again. Anyone else experience this?