Climate:
Ottawa has a humid continental climate (Koppen Dfb) with a range of temperatures from a record high of 37.8 °C (100 °F), recorded July 4, 1913, to a record low of -38.9 °C (-38 °F) recorded on December 29, 1933. This extreme range in temperature allows Ottawa to boast a variety of annual activities-more notable events such as the Winterlude Festival on the Rideau Canal in the winter and the National Canada Day celebrations on Parliament Hill in July. Ottawa had the fourth coldest temperature recorded in a capital city (after Ulaanbaatar, Mongolia; Astana, Kazakhstan and Moscow, Russia). It is the seventh coldest capital in the world by annual average temperature, and third coldest capital by mean January temperature.
The city experiences four distinct seasons. Summers are warm and humid in Ottawa. The average July maximum temperature is 26 °C (80 °F), although daytime temperatures of 30 °C (86 °F) or higher are commonplace. During periods of hot weather, high humidity is often an aggravating factor, especially close to the rivers. Ottawa averages many days with humidex (combined temperature & humidity index) between 30 °C (86 °F), and 40 °C (104 °F) annually. The highest recorded humidex was 48 °C (118 °F) on August 1, 2006.
Spring and fall are variable, prone to extremes in temperature and unpredictable swings in conditions. Hot days above 30 °C (86 °F) have occurred as early as March (as in 2002) or as late as October, as well as snow well into May and early in October (although such events are extremely unusual and brief). Average annual precipitation averages around 940 millimetres (37 in). The biggest one-day rainfall occurred on September 9, 2004 when the remnants of Hurricane Frances dumped nearly 136 millimetres (5.4 in) of rain in the city. The all-time monthly record is 243.4 mm (13.75 inches) set in July 2009. There are about 2,060 hours of average sunshine annually (47% of possible).
Snow and ice are dominant during the winter season. Ottawa receives about 235 centimetres (93 in) of snowfall annually. Its biggest snowfall was recorded on March 3-4, 1947, with 73 centimetres (2.4 ft) of snow. The average January temperature is -10.8 °C (12.6 °F), although days well above freezing and nights below -30 °C (-22 °F) both occur in the winter. The 2007-08 winter season snowfall (432.7 centimetres (170.4 in)) came within 12 cm (5 inches) of the record snowfall set in 1970-1971 (444.1 cm / 174.8 inches). High wind chills are common, with annual averages of 51, 14 and 1 days with wind chills below -20 °C (-4 °F), -30 °C (-22 °F) and -40 °C (-40 °F) respectively. The lowest recorded wind chill was -47.8 °C (-54 °F) on January 8, 1968.
Freezing rain is also relatively common, even relative to other parts of the country. One such large storm caused power outages and affected the local economy, and became known as the 1998 Ice Storm.
Destructive summer weather events such as tornadoes, major flash floods, extreme heat waves, severe hail and remnant effects from hurricanes are rare, but all have occurred in the Ottawa area. Some of the most notable tornadoes in the region occurred in 1978 (F2), 1994 (F3), 1999 (F1), 2002 (F1), 2004  and west end Ottawa 2009 (F0).