I got my chicks at the beginning of August, and I think if I didn't have a heat lamp, they would have died by now. The lamp got unplugged one night a week or so ago, and when I woke up in the morning, they were huddled and shivering in the corner, and one was almost dead in the opposite corner. I put her in quarantine with a lamp and gave her vitamins ans she was back to normal, but it still scared me! It's 70s to low 80s here during the day ad high 50s to 60s at night, so not even very cold (warm for the PNW!). There is no way I'd suggest doing chicks without a head lamp unless you keep them in your house and keep the house at 90 degrees.