The Köppen code that describes Denver, Colorado, is BSk, a cold semi-arid climate.
In the Köppen system, B identifies dry climates and S indicates a steppe or semi-arid climate. The final letter, k, means the location has a relatively cool average annual temperature. Denver receives more precipitation than many desert regions, but its high elevation, low humidity, and strong evaporation keep it in the semi-arid category.
Denver sits on the High Plains at the foot of the Rocky Mountains. The mountains strongly influence its weather, but the city itself lies east of the main crest and often sits in a precipitation shadow. Chinook winds can produce sudden winter thaws, while summer afternoons frequently bring thunderstorms and occasional severe hail.
The nearby climate classifications can cause confusion. Some surrounding or more humid microclimates may be described as Dfa or Cfa depending on the exact location and temperature threshold used. Those codes do not replace the standard classification for Denver proper, which is BSk.