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The weather

During the Winter War

Part I

 

The main sources:
"Suomen meteorologinen vuosikirja 1939, osa 1 ja 2", by Ilmatieteellinen keskuslaitos, Helsinki 1953
(The Meteorology Yearbook of Finland 1939, vol. 1 and 2)

"Suomen meteorologinen vuosikirja 1940, osa 1 ja 2", by Ilmatieteellinen keskuslaitos, Helsinki 1955
(The Meteorology Yearbook of Finland 1940, vol. 1 and 2)

Nowadays the "Ilmatieteellinen keskuslaitos" is the "Ilmatieteen laitos" or "Finnish Meteorological Institute". http://www.fmi.fi
The Yearbook's are available for public at the Institute's library, in Helsinki.

All graphic charts are based on the records of the above-mentioned publications, unless noted otherwise.

As additional sources, I've used the article "Pakkastalven kourissa" by Jyri Paulaharju in the "Talvisodan Pikkujättiläinen", p. 289 - 298
and an article by Professor J.Keränen titled "Säät sotatalvena 1939 - 1940", of which I received a copy by a clerk in the FMI's library.

 

Part I

 

Part II

  • Celsius-Fahrenheit conversion tool
  • Reference Map
  • Rainfall
        December
        January
        February
        March
    Monthly rainfall, winter 1939 - 1940
        The long time average rainfall
  • Snow cover
        Reported snow depths
        The thickness of the snow cover in some locations during the Winter War compared to a 30 year average
        Snow cover in mid- and southern Finland on 15 March 1940
  • Daylight
  • Wind
        Windchill

 

Foreword

 

The purpose of this article is to shed some light on the notorious weather conditions in which the Winter War was fought. Much has been written about the snow thickness during the Winter War. It's quite common to see some Soviet / Russian sources claiming that the snow was on occasion several meters deep, even in some rather recent works. E.g. the article of V.N.Baryshnikov (p.201, in "Talvisota, Venäjä ja Suomi",1989), where he writes that "..the general attack, which started on 11 February 1940 proceeded well in the circumstances of the extraordinary cold winter where the temperatures dropped to minus 40 - 45 Celsius and the snow being even 2 meters deep."
In many other books, mainly by Russians, which are either written about the Winter War or which mention it briefly, the weather is often quickly bypassed with a comment "...several meters of snow and - 40 degrees Celsius".

While the latter part has some truth in it as the temperatures indeed on occasion were even below -40 C, the first part about the thickness of the snow cover is a wild exaggeration. While the temperatures during the 1939-1940 winter were below long time average temperatures, the rainfall was less than average.

And as Mr. Baryshnikov is referring to the attack of the 7th and 13th Army in the Karelian Isthmus, the information is somewhat misleading. The very cold -40 to -45 Celsius temperatures occurred in mid-January, during the so-called trench war phase of the war, when the front in the Karelian Isthmus was static. At the time when the February offensive started, the snow cover was not even close to 1 meter (in fact the thickest snow cover in the Finnish weather stations on 15 Feb 1940 was 64 cm, at the station of Tohmajärvi some 65 km southeast from Joensuu).

As a matter of fact, no sudden warm period occurred which would have melted snow considerably, and if compared to the reported Reported snow depths or Snow thickness on 15 March 1940, one has to conclude that the source, which Mr. Baryshnikov used, has some rather questionable snow thickness figures.

 

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Celsius-Fahrenheit conversion tool

All temperatures on this page are in Celsius.
The below thermometer can serve as a quick conversion tool into Fahrenheit


If you want an exact, from Celsius to Fahrenheit conversion, use the below formula (The "C" is the temperature in Celsius):
(9 / 5) x C + 32

 

Reference Map

Due to the war, nearly all records from the weather stations at or near the border are unavailable (lost in the war, station evacuated or some other similar reason). As an effort to get a good overall picture, I've tried to use information from several stations around Finland, mainly in the North-South axis. The towns on the right are the towns named in the figures below.

In most cases, the towns mentioned in the figures are sorted "from South to North", i.e. starting from Helsinki and ending in Sodankylä or Utsjoki.

The towns, which are mentioned in this article

 

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The weather of the Winter War at a weekly basis
(in general)

Based mostly on the timeline found at "Talvisodan Pikkujättiläinen", p.163 - 179

 

Thursday 30 November 1939 - Sunday 3 December 1939

The war began in mild temperatures. Helsinki had +2 Celsius and Vyborg 0 Celsius. In Ladoga Karelia at Loimola (east of Sortavala), the temperature was -2.8 Celsius and some 10 cm of snow. By Sunday, the temperatures dropped a little, still being near 0 in most parts of the country. Up north in Sodankylä Lapland however, the temperature fell rapidly on Friday to -23.4 Celsius (at 21:00 PM) but the next evening (2 Dec) warming to a milder -10.4 Celsius and to -3.7 Celsius on Sunday evening.


Monday 4 December 1939 - Sunday 10 December 1939

The second week of the war started off in somewhat mild temperatures until it started to get cold on 8 December. After two days of cold (coldest temperature in Sodankylä was -19.9 Celsius), it got a little warmer on Sunday, being -8 C in Helsinki, -11.2 C in Sortavala and -8.1 C in Sodankylä.


Monday 11 December 1939 - Sunday 17 December 1939

The third week of the war began with two days of cold (ranging from -6.4 to -16.4 Celsius at Sodankylä in Lapland to around -10 Celsius in Sortavala). On Wednesday, the cold receded and the temperatures for the next two days throughout the country were roughly from 0 to -7 Celsius. On Friday it got a little colder again, until on Sunday the wind brought warm air from the Southwest which brought temperatures throughout Finland close to zero Celsius, even above it in many places.


Monday 18 December 1939 - Sunday 24 December 1939

Up to this fourth week, the temperatures had been relatively mild, considering usual winter time temperatures. Monday and Tuesday were very mild days, during which the warmest days of December were recorded in most parts of Finland (+3 Celsius in Viipuri and Helsinki, +2.2 Celsius in Sortavala and even +3.3 Celsius in Sodankylä Lapland). But on 20 December the temperature started to drop sharply (on average to about -4 C in the Aaland Islands, -7 C in Helsinki, -10 C in Viipuri, -14 C in Sortavala and about -14.5 C in Sodankylä). On Thursday it snowed almost throughout Finland, which continued on Friday warming the weather. But on Saturday it got cold again. On Christmas Eve Helsinki had -15 C, Viipuri -18 C, Sortavala -22 C and -27 C in Sodankylä.


Monday 25 December 1939 - Sunday 31 December 1939

The last week of the year 1939 (fifth of the war) started off in cold temperatures. In many parts of the country Monday and Tuesday were the days when the coldest temperatures so far were reached. On 25 December, -23 C was measured in Kuopio and Jyväskylä while on 26 December -19 C was measured in Helsinki, -25 C in Viipuri, -26 C in Sortavala, -29 C in Kajaani and -23 C in Oulu and -29 C in Sodankylä.
On the next days, the temperatures varied widely, when Southern Finland got warmer while Lapland got colder, the coldest temperature of December that was measured in Sodankylä was on the last day of the year being -34.3 degrees below zero.


Monday 1 January 1940 - Sunday 7 January 1940

The year 1940 (and the sixth week) began in the clutches of cold but mostly sunny weather, the temperatures being around -20 degrees below zero elsewhere except in the Aaland Islands where the temperature was considerably higher. The next day, on Tuesday, the cold receded when it began to snow everywhere. In Ladoga Karelia, the wind was blowing from the Lake Ladoga (even 20 m/s wind speeds were measured) clogging the roads in the area. The next day dawned with a sunny weather only to see the strong wind and the snowfall to start again. The Finnish 12th Division weather station measured the wind speed: 11 m/s while the temperature was -11.8 Celsius. After the snowfall ended, the temperature got colder again. On Saturday, 6 January, the temperatures were around or below -20 Celsius (-23 C in Viipuri, -26 in Oulu and -23 C in Sodankylä).


Monday 8 January 1940 - Sunday 14 January 1940

Seventh week. While Monday was still quite cold, the weather got warmer again on Tuesday. The next five days were relatively mild, rising by Saturday even above zero in most parts of Finland (the warmest period of January, 12 January the warmest recorded temperatures were: +3 in Viipuri, 0 in Kuopio, +1 C in Kajaani and +1 C in Sodankylä. On 13 January there was +4 C in Helsinki and +2 C in Jyväskylä). It also snowed in most parts of Finland (according to the Finnish 12th Division records, "+0.4 Celsius and sleet"). On Sunday the wind changed and cold air began to come from the north.


Monday 15 January 1940 - Sunday 21 January 1940

The eighth week of the war was the coldest week of the winter 1939-1940. It was this week that made the weather of the Winter War notorious.
For 4 consecutive days, from Monday to Thursday, the temperature was extremely cold due to a wind blowing from the northeast and north.

17 January was the coldest day of the war and at least the following places recorded their lowest daily temperatures: -33 C in Helsinki, -38 C in Viipuri, -38 C in Jyväskylä and -38 C in Kajaani. On other places, like in Koivisto (in the Karelian Isthmus, on the shore of the Gulf of Finland), the temperature in the morning was a numbing -45 degrees below zero, and in Summa before dawn, a -49 Celsius temperature was reported, while in Taipale the temperature around noon was -39 Celsius. In Ladoga Karelia, -42 Celsius was measured in Loimola.
(Note that the temperatures measured in the morning were much colder than the temperatures measured during the day, i.e. the noon temperature in Summa was above -49 below zero, while the temperature in Taipale before sunrise was probably below -39 Celsius.) On this day the whole Lake Ladoga froze.

On Friday, the temperatures rose about 10 degrees, being -20 C in Viipuri and -23 C in Sodankylä


Monday 22 January 1940 - Sunday 28 January 1940

The ninth week of the war started in temperatures ranging from about -10 Celsius in Southern Finland to about -30 Celsius in Lapland (-27 C in Sodankylä). Up north in Lapland the temperatures remained cold while the worst cold had receded from the mid and southern parts of Finland. 23 January was the coldest day of January in Sodankylä, -38.1 degrees below zero.


Monday 29 January 1940 - Sunday 4 February 1940

The tenth week was similar to the previous week, around -10 Celsius in the southern parts of Finland. Later in the week it got a little colder.


Monday 5 February 1940 - Sunday 11 February 1940

The 11th week was quite cold (temperatures fluctuating from about -10 C to -20 C in most parts of Finland). During the week all of Finland received snow. Friday was the coldest day of the week for mid- and southern Finland, Helsinki having -24 C, Kuopio - 20 C, while the in Lapland it got warmer, Sodankylä having only 9.5 Celsius (the mild period in Lapland continued to 12 February, on Saturday evening Sodankylä had a mild temperature of -3.5 degrees below zero).

On 11 February, the day when the Great Offensive of the Red Army in the Karelian Isthmus began, the temperatures throughout most of the Karelian Isthmus about -20 Celsius.


Monday 12 February 1940 - Sunday 18 February 1940

While heavy fighting was going on in the Karelian Isthmus, the temperatures during the 12th week of the war, varied from about -10 C to -24 C. On 15 February it got colder in the eastern part of Finland, Kuopio having -29 C and Jyväskylä -33 C. In Sodankylä, the coldest morning (07:00 AM) temperature of February was measured on 17 February: -39.2 degrees below zero (the average 17 February temperature in Sodankylä was -31 Celsius).


Monday 19 February 1940 - Sunday 25 February 1940

While the 13th week of the war saw Lapland having a somewhat mild temperature, only -12 C in Sodankylä, further south the temperatures were on average around -20 degrees below zero.

On Friday, the wind shifted, starting to blow warmer air from the south and west, with the result that Helsinki had a +1 Celsius temperature on Saturday. A lot of snow fell during this week, most of it between 20 - 24 February. On Sunday, after the snowfall ended, the weather got colder again.


Monday 26 February 1940 - Sunday 3 March 1940

14th week. While the temperature on Monday was still subzero, on Tuesday it started to get warmer again with plenty of snowfall in eastern Finland. On 28 February, the warmest day of February was recorded in the following places: Aaland Islands +3 C, Jyväskylä +2 C and Kajaani +2 C above zero. In Lapland however, the weather remained cold for a few more days, around -15 degrees below zero.

On Sunday it started yet again to get a little colder. -6 C in Helsinki, -5 in Oulu and -7 in Sodankylä. At the same time Lapland received some snowfall.


Monday 4 March 1940 - Sunday 10 March 1940

On the 15th and last full week of the war, the wind changed yet again and cold air began to pour from the north. This kept the temperatures well below zero degrees, Friday being the coldest day of the week (Helsinki -8 C, Kuopio -9 C, Oulu -19 C and Sodankylä -12 degrees below zero).


Monday 11 March 1940 - Tuesday 13 March 1940

Both Monday and Tuesday were days when there was a lot of snowfall in South Finland, especially in Southeastern Finland, and on Tuesday mostly around Viipuri. On 13 March, Helsinki had -10 C, Kuopio -14 C, Oulu -16 C and Sodankylä -24 degrees below zero.

 

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Temperatures

 

As mentioned in the Foreword-section, the temperatures of the Winter War are notorious. Unfortunately, the Finnish front-line units did not keep detailed records of the daily temperatures (or the changes within a day). Therefore, the best source are the Finnish Meteorological Institute's records, even though they lack information from the weather stations located at the prewar border (and thus located at or near battlefields). However, for a general view, the available data is enough.

 

The 5-day average temperatures
(Calculated by adding up daily averages (07.00 A:M + 15.00 P:M + 2 x 21.00 P:M x 1/4), and dividing the result by the number of days)



The above chart gives a somewhat clear picture of the cold periods of the war. Most notable is that the first cold period started only a few days after the first Red Army attacks against the Mannerheim Line (in the Karelian Isthmus, referring to the temperatures of Viipuri / Vyborg) were already repulsed. The very cold period, of which the Winter War is notorious, took place around mid-January, during which time the Red Army was not conducting any notable offensive actions. On the contrary, at that time frame, it was the Finnish IV Corps in Ladoga Karelia, which was conducting offensive operations against the 8th Army.

Note that unfortunately, due to the war, the records from the stations in Sortavala and Viipuri don't cover the whole war.

 

 

 

 

The average temperatures during the Winter 1939 - 1940

The average temperatures, Winter 1939-1940

 

The long time average temperatures

The Finnish information is from the years 1901-1930
The Russian information is from a longer time periods, see the notes below the figure

Long time average temperatures

* = The source for the average temperatures of the named Russian cities is from www.worldclimate.com
The Moscow data is derived from months between 1779 and 1991
The Kursk data is derived from months between 1891 and 1990
The Volgograd (Stalingrad) data is derived from months between 1951 and 1981

 

One of the factors, which perhaps contributed to the feeling of extreme cold was the sudden change of temperature. As an example, on 8 December, the day began with a pretty mild temperature, being -1.6 Celsius at 7:00 AM, but during the day, the temperature fell to -13.7 Celsius. Such a drop is certainly an unpleasant surprise. Another good example is 20 December, when the difference between the warmest and coldest temperature was 14.3 Celsius.

 

Day
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
7:00 AM
+0.3
-2.0
-1.9
-2.0
-1.3
+1.4
+0.2
-1.6
-13.6
-13.2
-12.6
-5.2
-4.8
-9.4
-5.8
-4.6
-5.4
-1.0
+1.0
-8.4
-18.3
-5.4
-11.4
-23.4
-18.0
-25.2
-12.5
-13.0
-14.5
-2.5
-6.8
15:00 PM
-0.2
-2.8
-3.4
-2.8
+1.2
+0.6
0.0
-7.0
-11.4
-13.2
-13.8
-3.6
-6.6
-6.0
-3.6
-3.8
-2.2
0.0
+0.1
-16.0
-18.6
-4.6
-12.4
-24.5
-16.5
-20.8
-16.0
-11.8
-7.8
-1.9
-11.4
21:00 PM
-0.6
-3.3
-3.4
-2.2
+1.2
+0.3
-0.4
-13.7
-12.5
-11.2
-9.8
-3.4
-8.4
-5.8
-4.0
-4.5
-1.8
+1.6
-3.6
-16.8
-20.4
-5.6
-20.0
-18.0
-20.8
-17.8
-16.2
-14.0
-5.6
-4.0
-11.3
Warmest
+0.3
-0.4
-1.4
-1.8
+1.8
+1.6
+0.4
-0.4
-10.8
-10.8
-9.2
-3.4
-3.2
-5.6
-3.6
-3.6
-1.6
+1.6
+2.2
-3.6
-16.8
-3.4
-5.4
-18.0
-16.4
-17.8
-11.9
-10.0
-5.6
-1.6
-4.0
Coldest
-1.3
-3.3
-3.4
-3.4
-2.3
0.0
-0.4
-13.7
-15.7
-13.9
-13.8
-9.8
-8.4
-9.5
-6.1
-4.7
-5.7
-2.0
-3.6
-17.9
-20.9
-20.4
-20.0
-24.9
-20.8
-25.5
-17.9
-16.3
-19.3
-5.6
-16.5
(Source "The Meteorology Yearbook of Finland 1939, vol. 1", p.35)


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Effects on troops & equipment

 

While the cold affected both sides, the Finns did have a significant edge, namely prewar training. While the Red Army was more trained to operate in the steppes of Russia or the weather & terrain of central Europe, the Finnish Army had trained to fight in Finnish terrain and the Finnish weather, winter included. The skill of skiing was virtually universal among the Finns, while it was a rather rare skill on the Soviet side. The Finnish military equipment was generally good for winter conditions,e.g. the infantry tent with the stove and the Finnish uniform tunic with the greatcoat. Unfortunately the low level of prewar funding resulted in a severe shortage of these essential equipment in the Finnish Army once the Mobilization began.

The Red Army did also have good winter equipment, in fact some items valued even higher than their Finnish counterparts, namely the greatcoat and especially the felt boots. Unfortunately some Red Army units arrived to the Finnish front either without or with too few of them. Also skis were surprisingly rare among the Red Army units.

Both sides also suffered from similar technical problems, some of which could have been recognized with proper prewar tests. As the temperatures dropped below -30 Celsius, some lubricants (in e.g. artillery pieces or vehicles) started to freeze, as did the fluid in the recoil system in some artillery pieces. In some artillery weapons the carriage failed in the cold, as the structure couldn't withstand the extreme cold and the stress of firing. Both sides also had problems with artillery shells, as the fuses became unreliable (increasing the number of duds).

 

The cold also caused considerable losses. While the number of those Red Army troops, who froze to death in e.g. the forests in and near Suomussalmi and Raate is unknown, the number of soldiers evacuated due to frostbite injuries was close to 10 000 ("Talvisodan Pikkujättiläinen", p. 811).
The Finns did also suffer a high number of frostbite cases, some 5 000, during January, the coldest month. Some 2 000 of them were severe ("Talvisodan historia vol.4" ,p. 345). The most common reason of frostbite, on the Finnish side, was the boots. They were either poor civilian boots or, most often, military boots which were too small. The situation improved as proper boots were sent from the Home Front and the troops started to use captured Russian felt boots.

E.g. the Finnish 4th Jaeger Battalion, operating in Ladoga Karelia, took part in the Major Counterattack of the Finnish IV Corps, 6 - 17 January 1940.
On 7 January, the battalion was ordered to make a daring move deep behind enemy lines, to capture an important Pukitsanmäki hill. At the front-line, the battalion had to cross a road guarded by Soviet tanks. The Jaegers crossed the road successfully, but the tents had to be left behind. The battalion made it to the hill while the temperatures were -30 Celsius. The Jaegers took defensive positions while it got even colder. For three days, the Jaegers maintained their positions on the hill without supplies or tents. For warmth, they had to huddle around small campfires, carefully camouflaged with snow and branches (as the Jaegers were on the hill, the nearest Soviet troops were billeting in a nearby farm the distance being only a few hundred meters). Luckily for the Jaegers the enemy did not notice the battalion on the hill, so no combat casualties were sustained. However, in order to not alert the enemy, the campfires had to be kept small. The first few nights cost the Jaegers 46 men evacuated due to frostbite, a heavy toll to for already under-strength battalion. The next cold period, 16 - 18 January, cost the battalion another 19 men evacuated due to frostbite while combat casualties from the same time frame were 1 killed and 7 wounded.
(Source: "Jääkäripataljoona 4:n tehtävät ja vaiheet sodassa 1939-1940", p.17 - 23)

 

Billeting in the cold brought their own problems. The Finnish Army had its excellent cloth tent, which was heated by a portable stove. The only problem was the severe shortage of them. As a substitute thousands of cardboard tents were manufactured, which were very clumsy consuming transportation capacity. Both sides also used civilian buildings for billeting where ever possible.

The Red Army enjoyed one definite advantage over the Finns in billeting. Due to the total Soviet air and artillery superiority, the Finnish troops couldn't heat up their shelters, houses or tents during daylight, except in bad weather. This was sorely felt during January in the shelters of the Mannerheim Line, as the heating of stoves produced smoke, which would have served as a target indicator for the Soviet artillery observers in their captive balloons.

 

The units of the Finnish Army were better suited for winter warfare than the Soviet units. The heavy equipment (lots of trucks, artillery, tanks) of the Soviet divisions kept them road-bound, while the lighter Finnish units were more maneuverable. The Finns relied mostly on horses. Horses consumed a lot of hay and had a rather poor cargo capacity, but the horses could move in snow where a truck got stuck.

Continue to Part II


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