We have become so accustomed to the mild weather since this fall that the arrival of cold weather may seem brutal to you. Indeed, next week, the cold arrives and with it various qualifiers such as “cold snap”, “cold wave”, which are sometimes used wrongly. However, cold waves in France are triggered in very specific weather configurations, and meet precise criteria from which we will be far away. Fortunately, the Weather Channel is here to help you see things more clearly.
The context: arrival of windy and humid maritime polar air
An air mass of polar origin will descend from the northwest over France © the Weather Channel
Next week will be marked by the arrival of an air mass from the far north, via Iceland. We speak of a “polar air stall”. This will be brutal and particularly marked, with an anomaly of 10°C below average at altitude. This air will also be very unstable, loaded with humidity after its passage over the sea. This will cause rain, snow showers and sleet, andheavy snowfall in the mountains. But this maritime origin will somewhat soften this air mass in the plain, where temperatures will be on average 3°C lower than seasonal norms.
In this cooled context, temperatures will be on average 3°C lower than the seasonal averages nationally, although it will be colder in the center-east and milder in the southwest.
A particularly gloomy and cold feeling
The temperatures felt will be low from next Wednesday © The Weather Channel
Certainly, you will not be very warm next week, especially from Wednesday onwards. The northwest wind will blow steadily with a risk of strong gust of wind in Hauts-de-France and in the mountains. The combination of gusts, showers and cold will give you a “frosty” feeling, more or less marked if you are cold. In the mountains, with the snow, you will have to be careful of this cold which can be difficult to bear outdoors. But this notion of feeling, at least at this stage, is not taken into account to define a “cold wave”.
Temperatures will be far from a cold snap
With the disrupted weather, temperatures will barely reach the frost threshold in the plains next week © The Weather Channel
The term cold snap doesn't just mean that it's going to be cold. This meets specific meteorological criteria, just like a heatwave in summer.
These criteria are mainly linked to the severity of the cold (frost, days without thawing and persistence of snow on the ground in the plains), its duration and its geographical extension. Among these criteria, temperatures must be 5°C lower than France-wide averages for several days, and the national thermal indicator must not rise above 0.9°C for several days ( for example, we will be at around +4°C next week), and that this indicator goes below -2°C for at least one day.
The national thermal indicator will fall below seasonal averages next week © The Weather Channel
These very negative temperatures must be generalized to several regions, or even to the entire country in certain situations. This was the case with the major cold waves in the winters of 1956, 1963, 1985 and 1987, or more recently in February 2012.
If these three conditions are met, we will speak of a cold wave. Conversely, if one of them is not, we will tend to speak of a cold snap.
We therefore deduce that a cold wave is not simply limited to mountain areas but mainly characterizes the plain areas of our country. Likewise, feelings do not come into play in this definition: only temperature forecasts and readings are objective criteria.
The cold will be marked in the mountains next week © The Weather Channel
Last widespread cold spell in France in February: February 2012
The last widespread cold wave across France for the month of February dates back to February 2012. The temperature had dropped to -25°C in Mouthe. Paris had experienced 6 continuous days without thaw and the temperature had plunged to -19°C in Orgerus (78), -15°C in Pontoise (78), -17°C in Romorantin and Bergerac, -11°C in Aubagne ( 13). On the morning of February 12, 2012, 3/4 of the country experienced temperatures below -10°C! We recorded -9°C and -8°C in Montpellier! We will still be quite far away from such low values in the north of France over the next few days!
As a reminder, the last cold snap in France dates back to January 2017 : it was a dry cold where the Loire carried ice cubes to Orléans and where the Allier was frozen.
The month of February 2018 was also marked by notable episodes of snow in the plains, particularly in the Paris region, and by a late cold snap at the end of February and beginning of March (the temperature had dropped to -10°C in inner Paris).
Last January, a cold period affected the regions north of the Seine with up to -14°C in Arras, even constituting a record for this station. But the duration of 3 days and the area concerned did not allow us to speak of a cold spell in the strict sense of the term.
You have understood, you will not be hot next week and you will have to cover up and turn on the heaters again if you have not already done so. But it will be a completely classic cold snap for this time of year, which we are no longer used to. Except in the mountains and the northeast, frosts will remain rare.
