Weather
- See also: Terrain
A dynamic counterpart to terrain, weather can affect movement and combat of all types of units. Weather has a big impact on logistics and how one is able to supply units. It should be noted provinces do not always have weather, and some provinces have no temperature modifers.
Night[edit | edit source]
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Night gives the following effects:
- -50% land attack[1]
- -20% air detection[2]
- -25% naval hit chance[3]
- Carrier aircraft cannot fly[3]
- -50% bombing targeting[3]
- +10% naval retreat speed[3]
- -90% close air support damage[4]
Weather types[edit | edit source]
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Weather can have an impact on the whole state or on single provinces.
State level[edit | edit source]
| Condition | Air Accidents Chance | Air Detection | Air Mission Efficiency | Carrier Traffic | Naval Detection | Naval Hit Chance | Naval Retreat Speed | Naval Speed | Naval Strike | Positioning | Ground Bombing Targeting | Organization loss when Moving | Supply Consumption Factor | Supply Factor | Truck attrition factor |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 Rain
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+10% | −10% | −10% | – | −10% | −5% | +5% | −5% | −20% | – | – | 5% | – | – | – |
 Storm
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+30% | −20% | −30% | −80% | −20% | −20% | +10% | −10% | −40% | −10% | −50% | 10% | 10% | −5% | – |
 Snow
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+10% | −15% | −10% | – | −15% | −5% | +5% | −5% | −30% | −10% | – | 10% | – | −10% | 30% |
 Blizzard
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+30% | −30% | −30% | −100% | −30% | −10% | +15% | −10% | −40% | −20% | −70% | 25% | 15% | −25% | 100% |
 Sandstorm
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+60% | −90% | −50% | – | – | – | – | – | −90% | – | −100% | 25% | – | −15% | 300% |
Province level[edit | edit source]
Temperature[edit | edit source]
| Condition | Heat Attrition | Winter Attrition | Division Attack | Division Breakthrough | Organization Regain | Organization loss when Moving | Entrenchment speed | Fleet speed while retreating | Supply consumption | Supply Factor | Truck attrition factor | Lower Bound in Degrees | Upper Bound in Degrees |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 Extremely cold
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– | +20% | −20% | −30% | −5% | – | −60% | +10% | – | −15% | 100% | -100 | -25 |
 Very cold
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– | +10% | −10% | −15% | – | – | −30% | +10% | – | – | – | -25 | -15 |
 Very hot
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+10% | – | – | – | −5% | – | – | – | – | −5% | – | 27 | 32 |
 Extremely hot
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+20% | – | −10% | – | −10% | – | – | – | +50% | – | 10% | 32 | 100 |
Note: Attrition from weather only applies if controller is at war.
While winter attrition can be reduced by appointing the armies to a commander with a 
Winter Specialist trait, there is no corresponding trait to reduce heat attrition. Commanders gain the Winter Specialist trait by fighting for a longer time in cold weather.
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Available only with the Together for Victory DLC enabled. |
South Africa has a unique focus Desert Equipment reducing heat attrition.
Ground conditions[edit | edit source]
| Condition | Attrition | Division Attack | Division Breakthrough | Division Defence | Division speed | Attacking division speed | Entrenchment speed | Organization Regain | Organization loss when Moving | Supply Factor | Truck attrition factor |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Snow | – | −20% | −15% | – | −20% | −25% | −5% | – | 10% | −20% | 50% |
| Deep snow | – | –40% | −30% | – | −50% | −50% | −15% | −5% | 25% | −40% | 100% |
| Mud | +70% | −40% | – | – | −50% | – | – | – | 25% | −15% | 500% |
| Flooding | – | – | – | +50% | −50% | – | −20% | – | 25% | −40% | 300% |
Very high snow will affect unit movement speed. Mud will increase attrition levels a lot as well as slow an army down to a crawl. A smart player will try not to attack The Soviet Union just as mud season begins or they might find a lot of their panzer divisions bogged down.
If the area is set up as being susceptible to mud during a particular time of year, and the water level over a time period is high enough, mud develops. Either rain or melting snow can be the source of the water. The game logs how much rain has fallen in a special region.
If the temperature is above 0, some of the stored water evaporates. The higher the temperature is, the higher the evaporation rate. If there is snow and the temperature is above 0, some snow will turn into water. The higher the temperature, the faster this conversion is. If there is mud (meaning there is a lot of water on the ground) and the temperature goes below 0, the mud disappears, because the water has frozen.
Weather effect descriptions[edit | edit source]
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This is a community maintained wiki. If you spot a mistake then you are welcome to fix it. |
Carrier Traffic -100% means that no planes from a carrier can fly.
Supply Consumption Factor - increases the supply use of a division in a state or province experiencing that weather.
Supply Factor - reduces the rate that supplies flow into a province in the state experiencing that weather.
Terrain effects on weather[edit | edit source]
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This is a community maintained wiki. If you spot a mistake then you are welcome to fix it. |
Some terrain makes it more or less likely for a weather effect to occur.
| Weather | Mountain | Plains | Marsh | Desert | Urban |
|---|---|---|---|---|---|
| Mud | -10% | +50% | +80% | +50% | |
| Snow and Blizzard
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+80% | -100% | -40% | ||
| Sandstorm
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-100% | +80% |
| Politics | Ideology • Faction • National focus • Ideas • Government • Puppet • Diplomacy • World tension • Civil war • Occupation • Intelligence agency |
| Production | Trade • Production • Construction • Equipment • Fuel |
| Research and technology | Research • Infantry technology • Support Companies technology • Armor technology • Artillery technology • Land doctrine • Naval technology • Naval doctrine • Air technology • Air doctrine • Engineering technology • Industry technology |
| Military and warfare | Warfare • Land units • Land warfare • Division designer • Tank design • Army planner • Command group • Commander • Battle plan • Combat tactics • Ship • Naval warfare • Aircraft • Air warfare • Experience • Officer corps • Attrition and accidents • Logistics • Manpower • Nuclear bomb |
| Map | Map • Province • Terrain • Weather • State |
| Events and Decisions | Events • Decisions |
- ↑ Defines NMilitary BASE_NIGHT_ATTACK_PENALTY = -0.5
- ↑ Defines NAir DETECT_CHANCE_FROM_NIGHT = -0.2
- ↑ 3.0 3.1 3.2 3.3 file Hearts of Iron IV\common\modifiers\00_static_modifiers.txt
- ↑ Defines NAir CAS_NIGHT_ATTACK_FACTOR = 0.1
