Home Island Presentation 13th September 2017
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Island Presentation

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The Climate

“This english translated version is made available for those who cannot read French. Translating from your own language into a foreign language is not an easy task, the translator is quite aware of its limitation and will welcome any suggestions. Thanks.”

The climate was so well described by Aubert de la Rüe, a geologist that spent several years in our islands that it is difficult to do better ! Unfortunately this poor translation won’t reflect this nice text.

“The climate of St. Pierre and Miquelon is rigorous but perfectly healthy. It is abnormally cold for the latitude, the mean average annual temperature is only 5°5 Celsius. This is due mainly to the polar air and cold marine waters brought in by the Baffin or Labrador current.

The absolute minima recorded in St. Pierre are between -20° and -22°. These are quite exceptional, temperatures usually do not reach below -15° to -17°, and only occasionally, every winter, it happens when cold air from Canada reach our islands, somewhat attenuated. Usually the temperatures are not that cold, but the high relative humidity and strong winds are an important chilling factors rendering cold hard to withstand.

Four months have average temperatures below zero, January and February being the coldest averaging in general -3° or -4°. During this period the thermometer varies from minus 10 and 5° above zero. The sea do freeze, but only exceptionally to the point of  impeding navigation around the islands. Nevertheless, drifting pack ice from arctic regions could be present from January to early April and surround the coasts, usually only for a few days, until wind and currents scatter them.

 

In spring, the temperatures rises very slowly and the air remains cold to the end of May, this explain the delayed growth of plants, the deciduous trees having leaves only in June. Temperatures below zero commonly occur at night in April and up to mid-May, sometimes later. However, from early June to autumn the temperatures are always above zero.

There are a few warm days in June, mostly with south-west winds, but the temperature rise only by the end of the month, to fluctuate from +10° to +20° during the summer, while the average do not go above 15°. If during this season the thermometer do not fall below + 7° it rarely reaches 22°. Occasionally temperatures of 29° have been recorded, they are quite exceptional.

 

Fairly cool days occur at times in September, but the frosts are quite rare and do not occur before the second fortnight of October. This month is often very nice with a few warm days. It is only by the end of November that frosts are pronounced enough to harden the surface of peat bogs. The ponds may start to freeze by then. Generally they do not freeze before mid-December, and remain frozen into March, sometimes to April. The salt ponds freeze later, only in January, and lose their ice earlier.

While the islands enjoy and oceanic climate, it presents rather important variations. The difference between the coldest month (February -4°) and the warmest (August 16°1) is over 20°. The diurnal thermal amplitude, from 5° to 10° is not too important, it is the speed with which changes occur that are hard to withstand. It is one of the remarkable aspects of our climate.

 

The relative humidity is high and do not vary much from one month to the next, being about 82 to 84% for the year. Winds from North and West are the driest, those from the south (SW to SE) the wetter.

The number of foggy days is important, due to the geographical location, near the meeting point of the cold waters of the Labrador current and the warm waters of the Gulf Stream. Their numbers varies from 85 to 120, and occur in each month in variable proportion. The number of hours of fog, averaging 50 in December, raises to 300 hours in July. The most unfavourable period, as far as fog is concerned spreads from the end of April to the end of July.

The atmospheric precipitations are abundant and the amount of water falling annually, as rain or snow, is 1328.5 mm. Dry years receive only about 1000 mm while rainy years can reach above 1500 mm. The heaviest rain showers occur with warm south-west wind. They can bring a total of 60 to 70 mm in 24 hours. The thundershowers, while not too violent are not rare in certain years.

The first flurries show-up in October, more usually in November, whitening the islands in an ephemeral way. The snow falls become more regular and more serious in December, but they rarely produce a permanent snow cover before the end of the month. The snow accumulation is quite variable from one year to the other. Generally it is in February and in early March that the snow cover is at its maximum. Due to violent winds the cover is quite unequal. In the woody areas of Miquelon and Langlade it could reach 0 m. 60 to 0 m. 75.

Some snow storms are quite violent, real blizzards, brought in by cold and dry North-easterly winds. On average the islands experience 2 or 3 of these storms every winter.

Thawing starts in March, this unpleasant period lasts for quite a while, it is more pronounced during the second fortnight. Generally most of the snow is gone by early April, sometimes thawing lasts until the middle of that month. Late snow falls, seen sometimes in May, can bring back for a few hours, or even days, a winter landscape.

In some ravines or sheltered slopes where the snow has accumulated to important depths, snow is sometimes still visible at the end of June. In that period, the peat bogs are sometimes still frozen to a certain depth, while they are totally thawed by the end of May.

The weather is quite variable and the speed of the changes are incredible. The high frequency of the wind is one of the important aspect of our climate. The atmospheric pressure is also extremely unstable, chiefly between October and June, this bring high winds. Most gales come with low pressure areas moving from west to east. In winter, their path are centred south of the islands bringing north-east gales sometimes to storm-force. In summer the lows are centred further north bringing south-west gales to storm-force. Winds starts from the south-east to end up north-west, through south and south-west.

The summer months are calmer, but strong disturbances, of tropical origin can affect the islands around mid-August. These tails of hurricanes could reach storm force.





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