July is the warmest month, with a daily average temperature of 74.2 °F (23.4 °C). Summers range from mild 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 a daily average temperature of 29.9 °F (−1.2 °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 can exceed 60 °F (16 °C) but also often fail to reach 32 °F (0 °C) during periods of cold weather and can even fail to rise above 0 °F (−18 °C) on occasion. On the coldest nights of the year, lows can easily 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 29, 2018. Due to the city's high elevation and aridity, diurnal temperature variation is large throughout the year.
Denver is in the center of the Front Range Urban Corridor, between the Rocky Mountains to the west and the High Plains to the east. Denver's topography consists of plains in the city center with hilly areas to the north, west and south. According to the United States Census Bureau the city has a total area of 155 square miles (401 km2), of which 153 square miles (396 km2) is land and 1.6 square miles (4.1 km2) (1.1%) is water. The City and County of Denver is surrounded by only three other counties: Adams County to the north and east, Arapahoe County to the south and east, and Jefferson County to the west.