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The cliamte description of Bylot Island comes from a 14 years database (1994-2007) recorded from our weather station located at 20 m above sea-level, in the Qarlikturvik Valley. Base Camp lake with Senecio congestus – lac du Camp de base avec Senecio congestus © Anna M. Calvert

Air Temperature

The average yearly temperature on Bylot Island is –14.5°C. Considering the summer months only (June-July-August), this average rises to 4.5°C whereas the winter (Dec-Jan-Feb) average is as low as –32.8°C.

The warmest month of the year is July, with an average of 6.2°C and the coldest month is January with an average –34.7°C.


From our data on air temperature, the number of degree-days above 0°C (or thawing degree-days, TDD) and the number of frost-free days have been calculated.

The number of degree-days above 0°C is a sum of all daily temperatures reaching above 0°C. It therefore represents heat accumulation, an important factor influencing plant growth and plant life events (such as flowering).On Bylot Island, the yearly number thawing degree-days averages 447 TDD. This means that the sum of all daily temperatures reaching above zero, over the entire year, averages 447.

On the island, the month with the highest number of thawing degree-days is July with an average 187 TDD.


Each year, organisms living on Bylot Island experience an average of 101 days where the air temperature is above 0°C. Obviously, the majority of these days occur in the summer months.


Soil Temperature

Soil acts as an insulator, consequently, soil temperatures are generally more tempered than the surrounding air temperature.

At a depth of 2 cm, the average yearly soil temperature recorded on Bylot Island is –10.2°C. In summer, this temperature rises above the air temperature to reach an average 4.6°C. This high temperature average for the summer is due to the fact that dark soil gathers heat from the sun.

In winter, the average soil temperature is –20.5°C. The coldest month for soil temperatures, at a depth of 2 cm, is February (–24.2°C) and the warmest month is July (7.3°C).

At a 10 cm depth, soil temperatures are even more isolated from the surrounding air. The yearly average at this depth is –11.1°C. In summer, the average rises to 0.7°C and during winter, it drops to –20.2°C.

The coldest month for soil temperature at 10 cm depth is March with an average of –24.2°C. The fact that the coldest average occurs in March and not in February, as observed for air temperature and soil temperature at 2 cm depth, may once again be explained by the insulating effect of soil cover which buffers soil temperatures.

At a 10 cm soil depth, the warmest monthly average still occurs in July. However, its 2.8°C average is considerably lower than the July averages for air and soil temperatures at a 2 cm depth.


Solar Radiation

Solar radiation is an important variable owing to its direct influence on living matter. Two kinds of solar radiations are recorded by the Bylot Island weather station. The first one, referred to as incident radiation, represents most solar radiation reaching the ground, either directly or indirectly by scattering, reflection or diffusion. It is measured in Joules per square meter per day, which represents how much energy reaches one meter of ground per day.

The second type of solar radiation measured by the station is known as Photosyntetically Active Radiation (PAR). In comparison with incident radiation, PAR can be more easily linked with plant activity since it represents the spectrum of light used by plants to photosynthesize. It is measured as total number of photons (energy particles) reaching one square meter of ground per day. PAR is measured in number of photons instead of energy units because one photosynthetic reaction occurs each time one photon is absorbed by a plant.

In the Arctic, the amount of solar energy input has large seasonal variations. Effectively, solar radiation ranges from almost zero input during the winter darkness, to exceptionally high inputs during times of continuous summer daylight.

On Bylot Island, the average yearly incident radiation is 8.3 MJ (Mega Joules)/m²/day and the total annual input of incident radiation can be summed to 3052 MJ/m²/year. During the winter, the average incident radiation input decreases to an average of only 0.1 MJ/m²/day but during the summer, the average is as high as 18 MJ/m²/day.

The month with the lowest incident radiation input is December with an average of 0 MJ/m²/day. Contrarily, June is the month with the highest average with 22.2 MJ/m²/day.


Phosynthetically Active Radiation follows the same pattern as incident radiation. The average yearly PAR input on Bylot Island is 17.2 moles of photons/m²/day and the total amount of PAR received yearly is 6509 moles/m².

During the winter darkness, the average PAR input is only 0.2 moles/m²/day and during the summer, it goes up to 34.1 moles /m²/day. The month with the lowest PAR input is December with an average of 0 moles /m²/day, and the month with the highest average PAR is May with 47.0 moles/m²/day.



On Bylot Island, summer precipitation is recorded manually. Indeed, data from the 1 June to the 17 August have been consistently recorded over the last 14 years. The average amount of precipitation, mostly rain, received between the 1 June and the 17 August is 94.3 mm.

For the rest of the year, the meteorological station provides a measure of snow thickness on the ground. For most of the year, snow cover remains thin, with an average of 13.5 cm. However, in May the snow cover increases dramatically to an average of 26.3 cm.


Wind Direction

Summer is the windiest season on Bylot Island, with an average wind speed of 10.4 km/h. Contrarily, the cold air mass of the winter is more stable and the wind speed average is 4.3 km/h. Through spring and fall, wind speeds are intermediate between the summer and winter with averages of 5.4 km/h and 7.6 km/h respectively.