I have seven, 4-week old chicks that I'd like to start putting outside during the day. I live in CA and the weather is a bit warm for this time of year (mid to upper 60's where I live) but in the 40's when I wake up in the morning. What's too cold for the babies? They have lots of feathers but they are not fully-feathered yet. Also, I do not have a way of putting light in the coop, it's far from electricity so I'd like to keep them inside until they can handle outside temps with out a heat lamp. Thanks!