How does temperature change in this game?

[I had a bad name 99]

Another edit:

I quote from the wikipedia: By 15 November 1941, the ground had finally frozen, solving the mud problem. The armored Wehrmacht spearheads, consisting of 51 divisions, could now advance, with the goal of encircling Moscow and linking up near the city of Noginsk, east of the capital.

The winter seems to help the attacker in its offensive. The Wehrmacht was eventually slowed down by fierce fighting at Tula. Though the lack of winter clothing did also cause a lot of attrition among the German attackers more (there is -20% attrition implemented in the game due to very cold temperature, and it affects only the attacker only*).



* In the wiki below, you can see that the attrition form weather only applies to controller (Germany), not state owner (USSR). So only attacker seems to be affected by attrition, unless both attacker and defender are fighting in the same state.

For example, in my current game, I am invading Germany, capturing a lot of territories. One such territory has me as the controller. If there is a winter, all equipment and manpower passing through it will suffer attrition. So my entire supply line can be affected by winter.

On the other hand, Germany is under attack, so the territories behind the frontline has it as the state owner, not controller. Attrition will not affect them.

Only if we fight in the same state, then the defender (Germany) will undergo attrition, but not me since I am not the state controller.

My troops in Japan will not suffer winter attrition because this part is me being a state owner, not state controller.

In other words, if you, as an attacker, are capturing huge amount of territories from the enemy, that amount of territories will be the area where your supply line is getting bushwacked by winter attrition. At the frontline though, it depends on who is state controller. You or enemy. Makes sense that the enemy (defender) can still suffer attrition if they launch their own counterattacks. Overall, the attacker will still suffer attrition more than the defender.

It will be cool to have a Winter DLC where you equip your divisions with winter clothing (something under support equipment like ski and stuff).

 

[I had a bad name 99]

Another edit: I controlled this state at the front lines. Meaning I will suffer attrition, and not the defender. It also means I can be more vulnerable to counter-offensive (which the Germans did suffer during Moscow counteroffensive)/

 

[DaleDVM]

200,000 German troops suffered from frostbite in the winter of 41-42.

I will just take Heinz Guderian's account as pretty accurate.

"The icy cold, the lack of shelter, the shortage of clothing, the heavy losses of men and equipment, the wretched state of our fuel supplies, all this makes the duties of a commander a misery."

"Only he who saw the endless expanse of Russian snow during this winter of our misery ... who drove for hour after hour through that no-man’s land only at last to find too thin shelter, with insufficiently clothed half-starved men; and who also saw, by contrast, the well fed and warmly clad and fresh Siberians, fully equipped for winter, only a man who knew all that can truly judge the events that now occurred."

 

[I had a bad name 99]

200,000 German troops suffered from frostbite in the winter of 41-42.

I will just take Heinz Guderian's account as pretty accurate.

"The icy cold, the lack of shelter, the shortage of clothing, the heavy losses of men and equipment, the wretched state of our fuel supplies, all this makes the duties of a commander a misery."

"Only he who saw the endless expanse of Russian snow during this winter of our misery ... who drove for hour after hour through that no-man’s land only at last to find too thin shelter, with insufficiently clothed half-starved men; and who also saw, by contrast, the well fed and warmly clad and fresh Siberians, fully equipped for winter, only a man who knew all that can truly judge the events that now occurred."

Well, that kinda proves my point about winter affecting attacker more in the game (weather attrition only applies to state controller at war ).

 

[Ffire]

200,000 German troops suffered from frostbite in the winter of 41-42.

I will just take Heinz Guderian's account as pretty accurate.

"The icy cold, the lack of shelter, the shortage of clothing, the heavy losses of men and equipment, the wretched state of our fuel supplies, all this makes the duties of a commander a misery."

"Only he who saw the endless expanse of Russian snow during this winter of our misery ... who drove for hour after hour through that no-man’s land only at last to find too thin shelter, with insufficiently clothed half-starved men; and who also saw, by contrast, the well fed and warmly clad and fresh Siberians, fully equipped for winter, only a man who knew all that can truly judge the events that now occurred."

Guderian is clearly not objective about that. He, as many german commanders of 41, is more to charge than winter for defeat : they just pushed too far exhausted troops. He, like most german former commander of WW2, tried to cover later his own responsability and mistakes with winter, Hitler interference, etc... The german propaganda and memorialist talked about temperature going -30, -40, and even -50. The meteo stations didn't recorded less than -17 (still, one night outside by -17 without proper equipment is more than enough to kill someone, and to let Guderian and other veterans a memory of misery). Soviet troops, for the vast majority, also lacked of proper winter clothing. The so famous Siberians didn't count for more than 2% of the soviet troops facing the werhmacht in front of Moscow.

 

[I had a bad name 99]

Okay, another good example of why weather CAN affect your decision to attack enemy units. While it does not determine the outcome of the battle, it can definitely slow you down (Especially important if you are rushing towards Moscow before winter sets in -- where you don't want to suffer attrition, which affects attacker mainly).

The sandstorm is causing a huge 50% debuff to my organisation, meaning I cannot attack as soon as I want to. Even though my combat strength is healthy.

 

[I had a bad name 99]

Guderian is clearly not objective about that. He, as many german commanders of 41, is more to charge than winter for defeat : they just pushed too far exhausted troops. He, like most german former commander of WW2, tried to cover later his own responsability and mistakes with winter, Hitler interference, etc... The german propaganda and memorialist talked about temperature going -30, -40, and even -50. The meteo stations didn't recorded less than -17 (still, one night outside by -17 without proper equipment is more than enough to kill someone, and to let Guderian and other veterans a memory of misery). Soviet troops, for the vast majority, also lacked of proper winter clothing. The so famous Siberians didn't count for more than 2% of the soviet troops facing the werhmacht in front of Moscow.

If I am not wrong, he is also quite the glory-hunt kind (Not to say I dislike that, as he is one of my favorite generals). After Battle of Smolensk, he and a few generals were eager to rush towards Moscow. Of course, many generals of that era were guilty of that too (Mark Clark, for example). I can't blame him for that. He is not a strategic player, more a tactical and operational one (like Rommel), eager to keep pushing forward and capture more territories. Whereas Hitler and the High Command have a strategic view, they knew the limitations of German logistics and that oil is more important to German war effort than Moscow. Moscow was already planned to be destroyed by the Soviet Command, having the insights of Napoleonic war.

 

[sekelsenmat]

Each strategic region has probabilities of weather conditions and temperature ranges set up for each calendar month. For example Moscow belongs to Central Russia (ID 133), so in December it has -17 to -3 degrees. The exact effects in each individual province are randomly generated from those ranges and the time of day. You can look them up in the game files, common/map/strategicregions.

Edit: and the weather effects shown like "extreme cold" etc. are produced based on this weather. I.e. "extreme cold" is anything below -25 or mud is generated based on temperature and accumulated rainfall. Those are defined in common/weather.txt.

I am trying to farm commando without invader, so I ran across this and the numbers there don't make sense to me....

strategic_region={
id=17
.....
weather={
period={
between={ 0.0 30.0 }
temperature={ 14.0 19.0 }
temperature_day_night={ 15.0 -15.0 }
....
period={
between={ 0.5 29.5 }
temperature={ 14.0 19.0 }
temperature_day_night={ 12.0 -12.0 }


In my game January temperatures in Ethiopia often go to 27 C, allowing to farm commando. But in January it always seems to be in the 15-20 range. But I opened the file map/strategicregions/17...txt and read the wiki and it makes no sense.

https://hoi4.paradoxwikis.com/Strategic_region_modding says:

temperature = { <min> <max> }
temperature_day_night = { <day> <night> }

• temperature scope determines the minimum and maximum temperature for the weather system.
• temperature_day_night scope determines the minimum and maximum temperature variability during day and night for the weather system.

So each day (actually it looks like every 2 days), the temperature for the whole strat region is selected as a random nr between {14 19} for january and { 14 19} for june. But in game I see high temperatures in January, never in June in Ethiopia.

Probably this is caused by the higher temperature_day_night. So it chooses for example in January 19 and in each province chooses an extra {0 15} number to add to that during the day? And {-15 0} to decrease at night? But decrease from the base {14 19} nr or from the day number {14 19} + {0 15}?

So the final temperature ranges are: {14 34} for january and {14 31} for june?

There is a very significant flaw in the model here in that terrain doesn't affect the temperature at all, and the regions are too big. Somalia in reality is very hot, but in game the strat region for it seems to represent the colder weather in mountainous Ethiopia. At the very least deserts should be hotter and mountains colder then the rest...

 

[bitmode]

So each day (actually it looks like every 2 days), the temperature for the whole strat region is selected

The temperature is calculated for individual provinces. For performance reasons, only 584 provinces (common/weather.txt: settings.performance.provinces_per_update) are updated per hour. With currently ~13K provinces total, this should result in an update every ~24 hours.

a random nr between {14 19} for january and { 14 19} for june. But in game I see high temperatures in January, never in June in Ethiopia.

The game gets the temperature in 4 steps:

1. take the minimum and maximum temperature from temperature = { <min> <max> }
2. modify them by the respective value (NOTE: the wiki is wrong in calling them <day> <night>) in temperature_day_night = { <min> <max> } scaled by -cos(time of day)
3. add a terrain modifier (currently unused)
4. choose a random temperature out of the resulting range and apply a drift (common/weather.txt:settings.temperature.variable) from the current temperature towards this temperature, but ensuring that the new temperature falls in the targeted range.

To get a better idea of how the temperature calculation works, I recommend temporarily setting performance.provinces_per_update to 14,000 and temperature.variable to 1. This way the first two steps can be seen more clearly, skipping the smoothing of step 4.

So it chooses for example in January 19 and in each province chooses an extra {0 15} number to add to that during the day? And {-15 0} to decrease at night? But decrease from the base {14 19} nr or from the day number {14 19} + {0 15}?

So the final temperature ranges are: {14 34} for january and {14 31} for june?

The day-night settings for (at least) Ethiopia make no sense (edit: fixed signs):

• minimum temperature in January at noon: 14 + -cos(pi) * 15 = 29
• maximum temperature in January at noon: 19 + -cos(pi) * -15 = 4
• minimum temperature in January at midnight: 14 + -cos(0) * 15 = -1
• maximum temperature in January at midnight: 19 + -cos(0) * -15 = 34

Using the above modified settings, I traced the min/random/max temperature in province 5041 (the desert province bordering Eritrea) for the first 12 hours of a game in a debugger:
min: 28.535, random: 21.098, max: 4.465
min: 27.020, random: 26.726, max: 5.980
min: 24.620, random: 12.911, max: 8.380
min: 21.575, random: 20.195, max: 11.425
min: 17.930, random: 15.700, max: 15.070
min: 14.015, random: 15.913, max: 18.985
min: 10.190, random: 10.518, max: 22.810
min: 6.545, random: 16.957, max: 26.455
min: 3.410, random: 22.992, max: 29.590
min: 1.040, random: 2.091, max: 31.960
min: -0.490, random: 31.824, max: 33.490
min: -1.000, random: 15.555, max: 34.000

So during the day, in an attempt to clip the resulting temperature to the min-max range, the game will always use the minimum temperature. Around sunset the temperature range becomes valid again but with a maximum temperature of 34, it may even become very hot at midnight!

The temperature values in June have slightly less crazy day-night settings so both at noon and midnight, very high temperatures become less likely.

Randomly clicking through other strategic regions shows many have a similar issue.

At the very least deserts should be hotter and mountains colder then the rest...

As mentioned above, terrain can in principle have a static effect on temperature. It is currently an unused feature though, see common/weather.txt:32. The comment there mentions that it should only be used if the effect were separated for day and night. But I think for at least hills and mountains it would make sense to use the feature as-is because they are generally colder both during day and night.

 

[Riekopo]

I don't know how weather is simulated in the game currently. But I do think there should be an option between historically accurate weather or a more random simulation of weather. I'm sure we have precise weather records for all the days of the war.

 

[Farquarsen]

When discussing Barbarossa in 41, the late start into the USSR in late June must also be calculated in the failure to reach Moscow as planned. The campaign season in Europe starts in late spring, usually in mid May after the mud ends. The Wehrmacht had to take care of Yugoslavia and Greece to secure logistical infrastructure because of Italy's failure to subjugate said territories. The delay proved fatal. Weather did have a determining factor as well as supply. Two shortcomings of the game that I am sure @podcat is aware of. I am confident one day within a future DLC, weather and logistics will be dealt with in a way that will bring balance and probable outcomes to the game.

 

[I had a bad name 99]

Weather seems to favor the defenders!