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 hosted the 2008 Democratic National Convention, which was the centennial of the city's first hosting of the landmark 1908 convention. It also hosted the G7 (now G8) summit between June 20 and 22 in 1997 and the 2000 National Convention of the Green Party. In 1972, 1981, and 2008, Denver also played host to the Libertarian Party of the United States National Convention. The 1972 Convention was notable for nominating Tonie Nathan as the Vice Presidential candidate, the first woman, as well as the first Jew, to receive an electoral vote in a United States presidential election.
In 2005, Denver became the first major city in the U.S. to vote to make the private possession of less than an ounce of marijuana legal for adults 21 and older. The city voted 53.5 percent in favor of the marijuana legalization measure, which, as then-mayor John Hickenlooper pointed out, was without effect, because the city cannot usurp state law, which at that time treated marijuana possession in much the same way as a speeding ticket, with fines of up to $100 and no jail time. Denver passed an initiative in the fourth quarter of 2007 requiring the mayor to appoint an 11-member review panel to monitor the city's compliance with the 2005 ordinance. In 2012, Colorado Amendment 64 was signed into law by Governor John Hickenlooper and at the beginning of 2014 Colorado became the first state to allow the sale of marijuana for recreational use.
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.