First time I ever went to Denver & Boulder in 2016, it was -6. The snow was beautiful but -6 was just awful. We also booked a walking brewery & distillery tour which was still on. It was fun but the walk from place to place was gnarly.
I lived in Littleton from Nov 2015 - June 2018. Never again. Brown dry and dead for most of the year, most of the precipitation is frozen... there is like one month of rain outside of the frigid months during which things grow.
My first year there I had no clue how to dress, I remember being at a bus stop pre-dawn, dressed for work with just an overcoat and gloves to add warmth IN -14.
As the stow fell and the wind blew it would have been beautiful if the leather soles on my shoes had not actually frozen.