This report describes the typical weather at the Ottawa Macdonald-Cartier International Airport (Ottawa, Ontario, Canada) weather station over the course of an average January. It is based on the historical records from 1977 to 2012. Earlier records are either unavailable or unreliable.
Ottawa, Ontario has a humid continental climate with warm summers and no dry season. The area within 25 mi of this station is covered by forests (73%), croplands (18%), lakes and rivers (3%), and built-up areas (3%).
The month of January is characterized by gradually falling daily high temperatures, with daily highs around 22°F throughout the month, exceeding 37°F or dropping below 3°F only one day in ten.
Over the course of January, the length of the day is gradually increasing. From the start to the end of the month, the length of the day increases by 53 minutes, implying an average day-over-day increase of 1.7 minutes.
The shortest day of the month is January 1 with 8:49 hours of daylight; the longest day is January 31 with 9:42 hours of daylight.
The earliest sunrise is at 7:25am on January 31; the latest sunset is at 5:07pm on January 31; the latest sunrise is at 7:43am on January 3; the earliest sunset is at 4:31pm on January 1.
Daylight savings time is observed in 2012 but it neither starts nor ends in January, so the entire month is in standard time.
The median cloud cover ranges from 89% (mostly cloudy) to 94% (mostly cloudy). The trend is for the sky to be clearing with the median cloud cover decreasing by 6% from the start to the end of the month.
On January 16, a representative day, the sky is clear or mostly clear 30% of the time, partly cloudy 4% of the time, and mostly cloudy or overcast 62% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around January 1, occurring in 76% of days. Precipitation is least likely around January 31, occurring in 69% of days.
Throughout January, the most common forms of precipitation are light snow and moderate snow.
Light snow is the most severe precipitation observed during 63% of those days with precipitation. It is most likely around January 4, when it is observed during 47% of all days.
Moderate snow is the most severe precipitation observed during 23% of those days with precipitation. It is most likely around January 1, when it is observed during 18% of all days.
The likelihood of snow falling is highest around January 3, occurring in 69% of days.
Accumulation at this location in January is just more likely than not. The chances of there being snow on the ground are highest around January 8, occurring 65% of the time.
The snow is typically at its deepest on January 22, with a median depth of 10.5"; the depth exceeds 21.7" only one year out of ten.
The relative humidity typically ranges from 57% (mildly humid) to 89% (very humid) over the course of a typical January, rarely dropping below 41% (comfortable) and reaching as high as 100% (very humid).
The air is driest around January 31, at which time the relative humidity drops below 65% (mildly humid) three days out of four; it is most humid around January 1, rising above 83% (humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a typical January, the dew point typically varies from -2°F (dry) to 18°F (dry) and is rarely below -22°F (dry) or above 34°F (dry).
Over the course of January typical wind speeds vary from 2 mph to 16 mph (light air to moderate breeze), rarely exceeding 23 mph (fresh breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around January 17, at which time the average daily maximum wind speed is 16 mph (moderate breeze).
The lowest average wind speed of 9 mph (gentle breeze) occurs around January 1, at which time the average daily maximum wind speed is 15 mph (moderate breeze).