I live in far north texas, and obviously colorado is much colder. But if u dont use a heat lamp normally, u Shouldnt need one with a broody and chicks. Mama hen will keep her chicks warm, frequently lowering her body to the ground so the chicks can scurry underneath her to warm up, and then scurry out again. If u do decide to let her hatch chicks in cold weather, just watch and make sure the chicks are strong & mobile enough to stay close to her for the first 48 hours or so. Especially the first 24 hours. Otherwise, a chick may become too cold, disoriented & die. I have sadly had that happen, when it was high temp 32 degrees with a gusty north wind on an early april day. I went out at sunset to lock up the laying hens, & saw the broody in her nestbox with all her chicks warmly snuggled inside. Well Almost all, because i noticed two chicks laying in a corner of their private broody pen. The chicks werent dead, but were cold, nearly comatose, & didnt survive despite my attempts to warm them up. (They were a little over 24 hours old at the time.) The only month my broodies havent hatched chicks (so far) is december. Currently have 4 broodies with chicks, another due to hatch this coming tuesday, and 1 in a wire dog cage broody jail. (Because she already hatched chicks this past summer, & enough is enough). All the seasons here have their pitfalls; springtime requires keeping the chicks protected from potential flooding rains, summer brings out the snakes which love to eat chicks, etc etc). If u decide to NOT let her hatch, do u have a crate/cage/safe place u could bring her inside your house/garage for 3-4 days? Thats usually sufficient time for the hormones to dissipate. I honestly think u may enjoy the broody hen & chicks experience more if u break her this time. She will likely go broody again in the spring, & meanwhile u will have time to better plan for the extra care that helping a hen sucessfully raise chicks entails. Also in the spring, if u dont locate fertile hatching eggs, your local feedstore will likely have baby chicks. Thats a whole 'nother topic, but giving her feedstore chicks to adopt and raise is yet another option. Having said all of the above, if u feel letting her hatch chicks is something u want to do Now, then by all means go for it!