Denver, where it's located

The climate of Denver, the capital and largest city of Colorado, is continental, with cold winters and hot summers. The city is located at a fairly low latitude (just below the 40th parallel), but very far away from the sea, and at 1,600 meters (5,250 feet) above sea level, on the eastern side of the Rocky Mountains. The result is a climate characterized by strong temperature changes between day and night, as well as by rapid changes in weather and temperature, depending on the prevailing air mass.
Another feature of Denver's climate is the chinook, the warm, dry wind that blows from the Rocky Mountains, and is capable of raising the temperature by several degrees. Due to this wind, the temperature can reach 15/18 °C (59/64 °F) even in winter, and 35/38 °C (95/100 °F) in summer.
In winter, the mountain sun warms up the air a lot, but in the evening, if the chinook doesn't blow, the temperature quickly drops below freezing.
The average temperature in December (which is strangely the coldest month, due to the lower frequency of the chinook) is -1 °C (30 °F), that of July is 23.5 °C (74 °F). Here are the average temperatures.
Denver - Average temperatures
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Min (°C)-8-7-31611151493-4-8
Max (°C)781216222832312619116
Min (°F)181927344352595748372518
Max (°F)454654617282908879665243

Precipitation in Denver is not abundant: just 365 millimeters (14.5 inches) per year. Winter is the driest season, while summer is the wettest, due to afternoon thunderstorms, sometimes accompanied by hail. Here is the average precipitation.
Denver - Average precipitation
MonthJanFebMarAprMayJunJulAugSepOctNovDecYear
Prec.(mm)101025455550554525251510365
Prec.(in)0.40.411.82.222.21.8110.60.414.4
Days45699889755480

Although the climate is fairly dry, the period in which it can snow is long (generally from mid-October to late April), so the amount of snow that falls in a year is considerable (on average, 137 cm or 54 inches).
Cold spells from Canada can be intense, and accompanied by blizzard blasts. Generally, the temperature reaches -20 °C (-4 °F) every year, but sometimes it can reach -30 °C (-22 °F) or below.
In summer, it is generally cool at night and hot during the day: between night and day, there are almost 20 degrees Celsius of difference (and sometimes even more). Given the high daily temperature range, even during the hottest periods, the nights remain cool or at least acceptable. Moreover, being that the humidity is low, the heat of day is bearable (but the sun beats down hard). In June 2018, the temperature reached 41 °C (106 °F), and 38.3 °C (101 °F) at the Centennial Airport, located south of the city, at almost 1,800 meters (5,900 feet).
In spring and autumn, it is generally cold at night and warm during the day. For example, in early October, it can still reach 28 °C (82 °F), but at night, it can already go down to the freezing point. Although it can snow in April and October, the snow generally melts quickly, because the temperature during the day exceeds freezing by a lot.

Denver

In Denver, the sun often shines all year round, and shines for a total of 3,100 hours. In particular, the winter sunshine is remarkable. Here are average sunshine hours per day.
Denver - Sunshine
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Hours778991110109866

When to go


Given the climatic instability and the strong temperature changes, it is difficult to find the best time to visit Denver, however, you can choose spring and autumn, and in particular, from mid-May to the beginning of June, and from mid-September to the beginning of October. However, summer is the best season to visit the Colorado mountains (unless you want to ski), since they are cold in the rest of the year.