Q: It's time to move my 5 week-old chicks to their outdoor coop, but it's cold outside! Will they be okay?
A: Sudden temperature changes are a real danger to your birds. You will need to make sure their transition outside doesn't shock them. Although chickens bear cold weather quite well, they will need to slowly acclimate themselves to the new conditions. For that reason, you may want to provide some sort of additional heat source and slowly lower the temperature every few days until it is about equal to your outdoor ambient local temperatures.
Remember, coops and brooders are very dusty, so double and triple check to make sure you're not creating a chicken coop fire hazard with your heat source. Heat lamps that get covered in dust or get too close to bedding can be a real danger!
Alternatively, you could consider transitioning them in a garage, 3-season porch or the like. We don't recommend providing a heated coop long term, for for short term use in the transition to the "big girl" coop, it is sometimes essential!