Denver lies within the semi-arid, continental climate zone . Humid continental and subtropical microclimates can be found. It has four distinct seasons and receives most of its precipitation from April through August. Due to its inland location on the High Plains, at the foot of the Rocky Mountains, the region can be subject to sudden changes in weather.
July is the warmest month, with an average high temperature of 89 °F (31.7 °C). Summers range from warm to hot with occasional, sometimes severe, afternoon thunderstorms and high temperatures reaching 90 °F (32 °C) on 38 days annually, and occasionally 100 °F (38 °C). December, the coldest month of the year, has an average daily high temperature of 46 °F (7.8 °C). Winters consist of periods of snow and very low temperatures alternating with periods of milder weather due to the warming effect of Chinook winds. In winter, daytime highs occasionally exceed 60 °F (16 °C), but they also often fail to reach 32 °F (0 °C) during periods of cold weather. Occasionally, daytime highs can even fail to rise above 0 °F (−18 °C) due to arctic air masses. On the coldest nights of the year, lows can fall to −10 °F (−23 °C) or below. Snowfall is common throughout the late fall, winter and early spring, averaging 53.5 inches (136 cm) for 1981–2010. The average window for measurable (≥0.1 in or 0.25 cm) snow is October 17 through April 27; however, measurable snowfall has fallen in Denver as early as September 4 and as late as June 3. Extremes in temperature range from −29 °F (−34 °C) on January 9, 1875, up to 105 °F (41 °C) as recently as June 28, 2018. Due to the city’s high elevation and aridity, diurnal temperature variation is large throughout the year.
Tornadoes are rare west of the I-25 corridor; however, one notable exception was an F3 tornado that struck 4.4 miles south of downtown on June 15, 1988. On the other hand, the suburbs east of Denver and the city’s east-northeastern extension (Denver International Airport) can see a few tornadoes, often weak landspout tornadoes, each spring and summer especially during June with the enhancement of the Denver Convergence Vorticity Zone (DCVZ). The DCVZ, also known as the Denver Cyclone, is a variable vortex of storm-forming air flow usually found north and east of downtown, and which often includes the airport. Heavy weather from the DCVZ can disrupt airport operations. In a study looking at hail events in areas with a population of at least 50,000, Denver was found to be ranked 10th most prone to hail storms in the continental United States. In fact, Denver has received 3 of the top 10 costliest hailstorms in United States history, which occurred on July 11, 1990; July 20, 2009; and May 8, 2017 respectively.
Based on 30-year averages obtained from NOAA’s National Climatic Data Center for the months of December, January and February, Weather Channel ranked Denver the 18th coldest major U.S. city as of 2014.
Denver’s official weather station is at Denver International Airport, roughly 20 miles from downtown. A 2019 analysis showed the average temperature at Denver International Airport, 50.2 °F (10 °C), was significantly cooler than downtown, 53.0 °F (12 °C). Many of the suburbs also have warmer temperatures and there is controversy regarding the location of the official temperature readings.