Climate

Christmas Lights - Parliament Hill

Ottawa has a range of temperatures from a record high of 37.8 °Celsius (100 °F) in the summers of 1986 and 2001 to a record low of -36.1 °C (-33 °F) being recorded in the winter of 1943, the second coldest temperature recorded in a capital city (after Ulaanbaatar, Mongolia). This extreme range in temperature allows Ottawa to boast a variety of annual activities and the requirement of a wide range of clothing. By annual average temperature, Ottawa is the seventh coldest capital in the world, however by mean January temperature, Ottawa ranks third behind Ulaan-baatar in Mongolia and Astana, Kazakstan.

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 4, 1947 with nearly 2.5 feet of snow (73 cm).^[4] Average January temperature is -10.8 °C (13 °F), although days well above freezing and nights below -25 °C (-13 °F) both occur in the winter. The snow season is quite variable; in an average winter, a lasting snow cover is on the ground from late November until early April, although some years are snow-free until around or beyond Christmas. 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 of -47.8 °C (-54.0 °F) on January 8, 1968.

Freezing rain is also relatively common, even if compared with other parts of the country. One such large storm caused power outages and affected the local economy, and came to be known as the 1998 Ice Storm.

Summers are fairly warm and humid in Ottawa, although they are typically short in length. The average July maximum temperature is 26.5 °C (80 °F), although temperatures of 30 °C (86 °F) or higher occur frequently. A maximum temperature of 39.5 degrees celsius (103 °F) was recorded in the summer of 2005 at certain locations. During periods of hot weather, high humidity is often an aggravating factor, especially close to the rivers. Ottawa annually averages 41, 12 and 2 days with humidex readings above 30 °C (86 °F), 35 °C (95 °F) and 40 °C (104 °F) respectively. The highest recorded humidex was 48 °C (118 °F) on August 1, 2006.^[5]

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 April or as late as October, as well as snow well into May and early in October (although such events are unusual and brief). Average annual precipitation averages around 943 millimetres (37 in.). The biggest one-day rainfall occurred on September 9, 2004 when the remnants of Hurricane Frances dumped nearly 5½ inches (136 mm) of rain in the city. There are about 2,060 hours of average sunshine annually (47% of possible).

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 before. Some of the most notable tornadoes in the region occurred in 1978 (F2), 1994 (F3, see Aylmer, Quebec) and 1999 (F1). On January 1, 2000, an earthquake measuring 5.2 on the Richter Scale struck Ottawa. However, it is very unlikely that F4 or F5 tornadoes like in the U.S. Plain States will occur since it is locating much farther away from the interaction of the airmass from both the Gulf of Mexico and the Rockies which can produce strong to violent tornadoes further south.

On February 24, 2006, an earthquake measuring 4.5 on the Richter Scale struck Ottawa. On average a small tremor occurs in Ottawa every three years. ^[6]

Дата добавления: 2015-07-20