Chapter 6.3: Weather System

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Introduction

DayZ has a fully dynamic weather system controlled through the Weather class. The system manages overcast, rain, snowfall, fog, wind, and thunderstorms. Weather can be configured through script (the Weather API), through cfgweather.xml in the mission folder, or through a scripted weather state machine. This chapter covers the script API for reading and controlling weather programmatically.

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Accessing the Weather Object

Weather weather = GetGame().GetWeather();

The Weather object is a singleton managed by the engine. It is always available after the game world initializes.

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Weather Phenomena

Each weather phenomenon (overcast, fog, rain, snowfall, wind magnitude, wind direction) is represented by a WeatherPhenomenon object. You access them through getter methods on Weather.

Getting Phenomenon Objects

proto native WeatherPhenomenon GetOvercast();
proto native WeatherPhenomenon GetFog();
proto native WeatherPhenomenon GetRain();
proto native WeatherPhenomenon GetSnowfall();
proto native WeatherPhenomenon GetWindMagnitude();
proto native WeatherPhenomenon GetWindDirection();

WeatherPhenomenon API

Each phenomenon shares the same interface:

class WeatherPhenomenon
{
    // Current state
    proto native float GetActual();          // Current interpolated value (0.0 - 1.0 for most)
    proto native float GetForecast();        // Target value being interpolated toward
    proto native float GetDuration();        // How long the current forecast persists (seconds)

    // Set the forecast (server only)
    proto native void Set(float forecast, float time = 0, float minDuration = 0);
    // forecast: target value
    // time:     seconds to interpolate to that value (0 = instant)
    // minDuration: minimum time the value holds before auto-change

    // Limits
    proto native void  SetLimits(float fnMin, float fnMax);
    proto native float GetMin();
    proto native float GetMax();

    // Change speed limits (how fast the phenomenon can change)
    proto native void SetTimeLimits(float fnMin, float fnMax);

    // Change magnitude limits
    proto native void SetChangeLimits(float fnMin, float fnMax);
}

Example --- read current weather state:

Weather w = GetGame().GetWeather();
float overcast  = w.GetOvercast().GetActual();
float rain      = w.GetRain().GetActual();
float fog       = w.GetFog().GetActual();
float snow      = w.GetSnowfall().GetActual();
float windSpeed = w.GetWindMagnitude().GetActual();
float windDir   = w.GetWindDirection().GetActual();

Print(string.Format("Overcast: %1, Rain: %2, Fog: %3", overcast, rain, fog));

Example --- force clear weather (server):

void ForceClearWeather()
{
    Weather w = GetGame().GetWeather();
    w.GetOvercast().Set(0.0, 30, 600);    // Clear sky, 30s transition, hold 10 min
    w.GetRain().Set(0.0, 10, 600);        // No rain
    w.GetFog().Set(0.0, 30, 600);         // No fog
    w.GetSnowfall().Set(0.0, 10, 600);    // No snow
}

Example --- create a storm:

void ForceStorm()
{
    Weather w = GetGame().GetWeather();
    w.GetOvercast().Set(1.0, 60, 1800);   // Full overcast, 60s ramp, hold 30 min
    w.GetRain().Set(0.8, 120, 1800);      // Heavy rain
    w.GetFog().Set(0.3, 120, 1800);       // Light fog
    w.GetWindMagnitude().Set(15.0, 60, 1800);  // Strong wind (m/s)
}

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Rain Thresholds

Rain is tied to overcast levels. The engine only renders rain when overcast exceeds a threshold. You can configure this via cfgweather.xml:

<rain>
    <thresholds min="0.5" max="1.0" end="120" />
</rain>

• min / max: overcast range where rain is allowed
• end: seconds for rain to stop if overcast falls below threshold

In script, rain will not visually appear if overcast is too low, even if GetRain().GetActual() returns a non-zero value.

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Wind

Wind uses two phenomena: magnitude (speed in m/s) and direction (angle in radians).

Wind Vector

proto native vector GetWind();           // Wind direction vector (world space)
proto native float  GetWindSpeed();      // Wind speed in m/s

Example --- get wind info:

Weather w = GetGame().GetWeather();
vector windVec = w.GetWind();
float windSpd = w.GetWindSpeed();
Print(string.Format("Wind: %1 m/s, direction: %2", windSpd, windVec));

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Thunderstorms (Lightning)

proto native void SetStorm(float density, float threshold, float timeout);

Parameter	Description
density	Lightning density (0.0 - 1.0)
threshold	Minimum overcast level for lightning to appear (0.0 - 1.0)
timeout	Seconds between lightning strikes

Example --- enable frequent lightning:

GetGame().GetWeather().SetStorm(1.0, 0.6, 10);
// Full density, triggers at 60% overcast, strikes every 10 seconds

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MissionWeather Control

To take manual control of weather (disabling the automatic weather state machine), call:

proto native void MissionWeather(bool use);

When MissionWeather(true) is called, the engine stops the automatic weather transitions and only your script-driven Set() calls control the weather.

Example --- full manual control in init.c:

void main()
{
    // Take manual control of weather
    GetGame().GetWeather().MissionWeather(true);

    // Set desired weather
    GetGame().GetWeather().GetOvercast().Set(0.3, 0, 0);
    GetGame().GetWeather().GetRain().Set(0.0, 0, 0);
    GetGame().GetWeather().GetFog().Set(0.1, 0, 0);
}

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Date & Time

The game date and time affect lighting, sun position, and the day/night cycle. These are controlled through the World object, not Weather, but they are closely related.

Getting Current Date/Time

int year, month, day, hour, minute;
GetGame().GetWorld().GetDate(year, month, day, hour, minute);

Setting Date/Time (Server Only)

proto native void SetDate(int year, int month, int day, int hour, int minute);

Example --- set time to noon:

int year, month, day, hour, minute;
GetGame().GetWorld().GetDate(year, month, day, hour, minute);
GetGame().GetWorld().SetDate(year, month, day, 12, 0);

Time Acceleration

Time acceleration is configured in serverDZ.cfg via:

serverTimeAcceleration = 12;      // 12x real time
serverNightTimeAcceleration = 4;  // 4x acceleration during night

In script, you can read the current time multiplier but typically cannot change it at runtime.

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WorldData Weather State Machine

Vanilla DayZ uses a scripted weather state machine in WorldData classes (e.g., ChernarusPlusData, EnochData, SakhalData). The key override point is:

class WorldData
{
    void WeatherOnBeforeChange(EWeatherPhenomenon type, float actual, float change,
                                float time);
}

Override this method in a modded WorldData class to intercept and modify weather transitions:

modded class ChernarusPlusData
{
    override void WeatherOnBeforeChange(EWeatherPhenomenon type, float actual,
                                         float change, float time)
    {
        super.WeatherOnBeforeChange(type, actual, change, time);

        // Prevent rain from ever going above 0.5
        if (type == EWeatherPhenomenon.RAIN && change > 0.5)
        {
            GetGame().GetWeather().GetRain().Set(0.5, time, 300);
        }
    }
}

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cfgweather.xml

The cfgweather.xml file in the mission folder provides a declarative way to configure weather without scripting. When present, it overrides the default weather state machine parameters.

Key structure:

<weather reset="0" enable="1">
    <overcast>
        <current actual="0.45" time="120" duration="240" />
        <limits min="0.0" max="1.0" />
        <timelimits min="900" max="1800" />
        <changelimits min="0.0" max="1.0" />
    </overcast>
    <fog>...</fog>
    <rain>
        ...
        <thresholds min="0.5" max="1.0" end="120" />
    </rain>
    <snowfall>...</snowfall>
    <windMagnitude>...</windMagnitude>
    <windDirection>...</windDirection>
    <storm density="1.0" threshold="0.7" timeout="25"/>
</weather>

Attribute	Description
reset	Whether to reset weather from storage on server start
enable	Whether this file is active
actual	Initial value
time	Seconds to reach the initial value
duration	Seconds the initial value holds
limits min/max	Range for the phenomenon value
timelimits min/max	Range for transition duration (seconds)
changelimits min/max	Range for change magnitude per transition

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Summary

Concept	Key Point
Access	GetGame().GetWeather() returns the Weather singleton
Phenomena	GetOvercast(), GetRain(), GetFog(), GetSnowfall(), GetWindMagnitude(), GetWindDirection()
Read	phenomenon.GetActual() for current value (0.0 - 1.0)
Write	phenomenon.Set(forecast, transitionTime, holdDuration) (server only)
Storms	SetStorm(density, threshold, timeout)
Manual mode	MissionWeather(true) disables automatic weather changes
Date/Time	GetGame().GetWorld().GetDate() / SetDate()
Config file	cfgweather.xml in mission folder for declarative setup

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Best Practices

• Call MissionWeather(true) before setting weather in init.c. Without this, the automatic weather state machine will override your Set() calls within seconds. Always take manual control first if you want deterministic weather.
• Always provide a minDuration parameter in Set(). Setting minDuration to 0 means the weather system can immediately transition away from your value. Use at least 300-600 seconds to hold your desired state.
• Set overcast before rain. Rain is visually tied to overcast thresholds. If overcast is below the threshold configured in cfgweather.xml, rain will not render even if GetRain().GetActual() returns a non-zero value.
• Use WeatherOnBeforeChange() for server-wide weather policy. Override this in a modded class ChernarusPlusData (or the appropriate WorldData subclass) to clamp or redirect weather transitions without fighting the state machine.
• Read weather on both sides, write only on server. GetActual() and GetForecast() work on client and server, but Set() only has effect on the server.

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Compatibility & Impact

Mod Compatibility: Weather mods commonly override WeatherOnBeforeChange() in WorldData subclasses. Only one mod's override chain runs per map's WorldData class.

• Load Order: Multiple mods overriding WeatherOnBeforeChange on the same WorldData subclass (e.g., ChernarusPlusData) must all call super, or earlier mods lose their weather logic.
• Modded Class Conflicts: If one mod calls MissionWeather(true) and another expects automatic weather, they are fundamentally incompatible. Document whether your mod takes manual weather control.
• Performance Impact: Weather API calls are lightweight. The phenomena interpolation runs in the engine, not in script. Frequent Set() calls (every frame) are wasteful but not harmful.
• Server/Client: All Set() calls are server-only. Clients receive weather state via engine synchronization automatically. Client-side Set() calls are silently ignored.

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Observed in Real Mods

These patterns were confirmed by studying the source code of professional DayZ mods.

Pattern	Mod	File/Location
MissionWeather(true) + scripted weather cycle with CallLater	Expansion	Weather controller in mission init
WeatherOnBeforeChange override to prevent rain in specific areas	COT Weather Module	Modded ChernarusPlusData
Admin command to force clear/storm via Set() with long hold duration	VPP Admin Tools	Weather admin panel
cfgweather.xml with custom thresholds for snow-only maps	Namalsk	Mission folder config

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