December climate: the month of the first cold waves

Monday 02nd December 2024 04:34 AM

December is the first month of winter, both meteorologically and calendrically, with the solsticewhich occurs around December 21 depending on the year. The days there are the shortest of the year, lasting around 8 hours in mainland France. We are therefore in the heart of the winter season, the feeling of which is accentuated by frequent grayness or fogs which tarnish the days even more.

The cold is the first marker of the months of December, with the first real snowfall in the plains depending on the year. Another marker of the months of December: the storms winter, sometimes remarkable. This year we are also commemorating the 20th anniversary of Lothar and Martin, the two “storms of the century” which hit our country hard at the end of December 1999, and which are among the most catastrophic weather phenomena in contemporary history in France.

Temperatures in December: the first cold waves

Although recent years have tended to have mild Decembers (since 2011, Decembers have been systematically milder than seasonal averages), the last month of the year is, statistically, the second coldest month in mainland France after January. However, the rapid drop in temperatures, which began in octoberslows down quickly with only an average difference of 1.5°C between the start and end of the month.

December is the month when real cold waves can appear in France. Some were remarkable with severe frost and blizzards in our country, particularly in the period between Christmas and New Year's Day. So, the terrible winter of 1962/1963considered the coldest of the 20th century, led to a freezing month of December with a first cold offensive in the first decade, before really taking hold on December 23. Closer to us, one of the last significant cold waves, those of January 1997, began in December 26, 1996. At that time, temperatures dropped to between -10°C and -15°C in the northeast of the country. If we remember December 2010, which was snowy in the plains, the oldest will remember the snow and ice storm which paralyzed the northern regions of the Loire on the evening of New Year's Eve 1978.

The exceptional snowstorm of December 31, 1978 in Ardres (62)

Going back into the archives, we note that the lowest temperatures observed in France were recorded during a month of December, that of the year 1879, when it was notably -24°C at Paris-Montsouris (the record absolute) and -35°C in Nancy!

Finally, the coldest regions are those with a semi-continental climate, in the east of France, with averages of around 0°C for the minimums (Dijon, Strasbourg) and 5°C for the maximums. The mildest regions are close to the Atlantic (from 4° to 5°C in the morning to 10° – 12°C in the afternoon on average) and especially around the Mediterranean, with 6.3° for the minimums and 13.8°C for maximums in Nice (06).

Extremes recorded in December since 1900

Climatic evolution for the month of December in France © The Weather Channel

France experiences extremes both in terms of cold and mildness. During this month, the extreme values are in fact between -30°C and 27°C, with a concentration of the lowest temperatures mainly around the 1930s and 1960s. There softness can also be remarkable. Occurring after the first cold weather in November, even more spectacular warm spells could often occur for Christmas, which is statistically milder than New Year's Day. We witnessed an astonishing series of “balcony” Christmases (that is to say particularly sweet) between 2011 and 2017, where numerous records were then broken, notably in 2015. On New Year's Eve, temperatures can reach 15°C in the northern half, as in Paris and Strasbourg in 2017. To date, the mildest end-of-year period since 1947 returns at the end of December 2021, between Christmas and January 1, 2022.

Extreme temperatures recorded in December since 1900

Min Max

-32.8°C, December 9, 1967 in Mouthe (25) 27.2°C, December 4, 1985 in Pau (64)

-25.8°C, December 18, 1933 in Clermont-Fd (63) 25.1°C, December 2, 1985 in Biarritz (64)

-24.6°C, December 22, 1938 in Lyon (69) 22.5°C, December 16, 1985 in Bordeaux (33)

-23.9°C, December 10, 1879 in Paris (75) 21.9°C, December 18, 1989 in Clermont-Fd (63)

-21°C, December 29, 1964 in Le Mans (72) 17.1°C, December 16, 1989 in Paris (75)

Historic storms

Winter storms hit France especially in January and February. Since 1980, of 30 major winter storms, about 20% have occurred in December. They were sometimes very violent, including those of December 1999, which remain engraved in memories as the “storms of the century”. These storms are mainly caused by the rapid circulation of Atlantic depressions, but some are still raging in the southeast with the latest Mediterranean episodes of the season.

Precipitation: the start of the snow season in the mountains

The month of December is statistically a rainy month in France, under the influence of the prevailing westerly oceanic winds laden with humidity. However, cumulative rainfall decreases slightly compared to the month of November, particularly in the south-east, where Mediterranean episodes become less frequent as the season progresses.

Statistically, the regions of the Atlantic coast are the wettest, while the eastern regions are the driest due to a more continental, cold and dry climate. Monthly accumulations vary almost threefold, with for example 50 mm on average in Strasbourg (67) compared to 150 mm in Biarritz (64). Finally, the month of December also corresponds to the average dates of first snowfall in the plains in the west and south (Bordeaux: December 15).

At the same time, the snow begins to thicken in the mountains: December truly marks the start of the snow season, with the Christmas school holidays on the horizon.

The most and least sunny regions in December

The sunniest regions are mainly coastal, from southern Brittany to Aquitaine and around the Mediterranean. This phenomenon is linked to the very changeable weather at the seaside, explaining beautiful clearings between disturbances. The Mediterranean area experiences fewer episodes of bad weather than in November, so that the sunshine there is the best in France. On the other hand, mountainous regions have more clouds hanging on their sides with less sunshine. The eastern regions also experience frequent gray days, under fog and low clouds, explaining these low levels of sunshine despite lower precipitation than elsewhere.

It happened in December

Devastating storms

– December 1999: two exceptional stormsbaptized Lothar and Martin, followed one another on December 25 and 27, which, statistically, is unusual. During Storm Martin on December 27, 1999, approximately 6% of the metropolitan area was hit by gusts greater than 160 km/h, which had never happened since modern records began. Maximum values reach 173 km/h at Paris-Orly, 198 km/h at the island of Oléron (17) and 205 km/h at Mandelieu La Napoule (06).

– 1952 : Wind gusts reached 184 km/h in Tours on December 12.

– 1962 : a Mediterranean storm reaches 216 km/h at Cap Corse.

– 1976 : an exceptional Atlantic storm causes gusts of 176 km/h in Millau and Quimper.

– 1979 : an Atlantic depression blows at 169 km/h at Cancale (35) while Cape Béar (66) records 194 km/h.

– End of December 1979: ocean storms follow one another. We note 158 km/h in Granville (50).

– The end of December 1991 is also stormy with gusts of 205 km/h at Cap Corse and 148 km/h at Cancale (35).

– 1997 : 180 km/h is observed in Leucate (11) during a Mediterranean storm.

Major floods

– End of December 2000repeated rains in Brittany, combined with a high tidal coefficient, cause major flooding in Finistère: Quimperlé, Morlaix and Landerneau are submerged and affected.

– Early December 2003major floods affect all rivers between the Loire and the Rhône, the Camargue is flooded. There are 7 victims.

Snowstorms and cold records

– December 10, 1879 in Paris (75), the “coldest day” in contemporary history, with -23.9°C recorded at Parc Montsouris.

– December 28, 1962, during the coldest winter of the 20th century, temperatures plunged to -19°C in Colmar (68) and -15°C in Auxerre (89).

– December 31, 1978: a blizzard broke out on the evening of New Year's Eve 1978 north of the Loire. In Paris, the temperature goes from +10°C in the morning, in the rain, to -10°C in the evening in the snow. Hundreds of motorists are stuck on the Normandy and Beauce roads. It’s the “white tide”.

– December 10, 1990the Rhône-Alpes region is paralyzed by snow: up to 70 cm falls in the plains. The same scenario occurred again in 1991: thousands of vacationers were stranded on the roads of the Alps, the ORSEC plan was launched.

– December 2010 is the coldest in 40 years, with snow on the plains until Christmas. At the beginning of the month, remarkable snowfall fell on the Channel coasts, with thicknesses close to 60 cm in Cherbourg (50). In Paris, we observed 16 days with snow on the ground and a record maximum thickness of 12 cm in Montsouris park. The cold is almost permanent but there are no real records for the month of December. However, the monthly average in France is 3°C lower than normal, which has not happened since 1969. We still recorded -18°C in Strasbourg on the night of December 25 to 26 and -15°C. C in Auxerre (89).