Mama hen took her new chicks outside.....one died from the cold temps....help!!

It's not unusual for mama hens to take young chicks outdoors in the cold.  They should get under her to warm up when they get cold.  My guess is, this chick did not die form cold.  If the others are OK, and she pays attention to them and covers them when they go under her, I would let her do her thing.

Put a light over them and lock them up.

This is one reason chickens in the wild often don't lay eggs and then sit on a clutch this early in the year...the light tells them when it's warm enough to begin starting a new family. We've circumvented that with artifical lighting and breeding for laying.

I would put the momma and babies in a spearate enclosure to protect them from the flock with enough room for her to eat, drink and poo. That way, she can do her business but not be too far from the chicks.

Agree totally with PP about that wild chickens do not hatch their eggs this early at all I am in Northern Wisconsin. I try not to allow my hens to brood at this time, I did this year, and my hen hatched out one of the 4 eggs she was on. So right away they both were moved into the house for 6 weeks!! LOL Mom made a mess of the floor with bedding from the Large dog kennel they were in, but its WAY to cold even with mom to sit on top of them to be outside, the wind itself here sometimes is hard on my adult chickens let alone a chick!

A 3 day old or 5 day old does not have its outside feathers at all! They shouldnt be getting wet or chilled at all. I would take her and the rest and put them in something lock them up. She will be fine you can always take her out of the pen and allow her to stretch her legs and then put her back with the chicks. I wouldn't let mom start showing the world to the chicks till they are feathered out. You more than likely will lose more if they dont get locked up for the time being.