The whole world doesn't have to be warm for baby chicks. They only need a warm spot to warm up under. The rest can be cold.
Imagine your chicks as little campers. They need a "campfire" at which to warm up when they get chilled. They go under the heat lamp or into a heating pad cave, get toasty warm, then when they are starting to get too hot, they leave and go where it's cool. This is called regulating their body temperature.
The fact is, it's much healthier for chicks to have a cool environment with a heat zone. When their entire brooder is kept very warm, they suffer from overheating.
Picture a broody hen sitting on eggs. The eggs hatch, and the chicks dry out under the hen. In just a few hours, the chicks are running around exploring their new world, and when they chill, they scoot back under the hen. It's 100 F under her, so they aren't going to remain under her all the time because they'd be too hot. In fact, chicks spend more time running around than they do under the hen. And the coop where they hatched is not normally heated, so this time of year in most places, it's about as cold as your place is.
So, don't worry about the chicks. Give them a heat source, make sure they don't have any drafts or dampness, and they'll do fine.
