Ottawa has a humid continental climate with four distinct seasons and is between Zones 5a and 5b on the Canadian Plant Hardiness Scale. The average July maximum temperature is 26.6 °C (80 °F). The average January minimum temperature is −14.4 °C (6.1 °F).
Summers are warm and humid in Ottawa. On average 11 days of the three summer months have temperatures exceeding 30 °C (86 °F), or 37 days if the humidex is considered. Average relative humidity averages 54% in the afternoon and 84% by morning.
Snow and ice are dominant during the winter season. On average Ottawa receives 224 cm (88 in) of snowfall annually but maintains an average 22 cm (9 in) of snowpack throughout the three winter months. An average 16 days of the three winter months experience temperatures below −20 °C (−4 °F), or 41 days if the wind chill is considered.
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. Annual precipitation averages around 940 mm (37 in).
Ottawa experiences about 2,130 hours of average sunshine annually (46% of possible). Winds in Ottawa are generally Westerlies averaging 13 km/h (8.1 mph) but tend to be slightly more dominant during the winter.
The highest temperature ever recorded in Ottawa was 37.8 °C (100 °F) on 4 July 1913, 1 August 1917 and 11 August 1944. The coldest temperature ever recorded was −38.9 °C (−38 °F) on 29 December 1933. The hottest daily low temperature was 25.0 °C (77 °F) on 9 July 1955. The coldest daily high temperature was −32 °C (−26 °F) on the same day as the record low. The hottest month on record was July 1921, averaging 25.0 °C (77 °F). The coldest month on record was January 1994, averaging −19 °C (−2 °F)