diff --git a/asm/field_screen.s b/asm/field_screen.s
index 6b49b9c7c1..1792b9cc8c 100644
--- a/asm/field_screen.s
+++ b/asm/field_screen.s
@@ -2472,15 +2472,15 @@ _080AC3B6:
 	bx r0
 	thumb_func_end play_some_sound
 
-	thumb_func_start sub_80AC3BC
-sub_80AC3BC: @ 80AC3BC
+	thumb_func_start IsWeatherChangeComplete
+IsWeatherChangeComplete: @ 80AC3BC
 	ldr r0, =gUnknown_02038454
 	ldr r1, =0x000006d3
 	adds r0, r1
 	ldrb r0, [r0]
 	bx lr
 	.pool
-	thumb_func_end sub_80AC3BC
+	thumb_func_end IsWeatherChangeComplete
 
 	thumb_func_start sub_80AC3D0
 sub_80AC3D0: @ 80AC3D0
diff --git a/asm/time_events.s b/asm/time_events.s
deleted file mode 100644
index de2d2d165f..0000000000
--- a/asm/time_events.s
+++ /dev/null
@@ -1,225 +0,0 @@
-	.include "asm/macros.inc"
-	.include "constants/constants.inc"
-
-	.syntax unified
-
-	.text
-
-	thumb_func_start GetMirageRnd
-GetMirageRnd: @ 8137890
-	push {r4,lr}
-	ldr r0, =0x00004024
-	bl VarGet
-	adds r4, r0, 0
-	lsls r4, 16
-	lsrs r4, 16
-	ldr r0, =0x00004025
-	bl VarGet
-	lsls r0, 16
-	lsrs r0, 16
-	lsls r4, 16
-	orrs r4, r0
-	adds r0, r4, 0
-	pop {r4}
-	pop {r1}
-	bx r1
-	.pool
-	thumb_func_end GetMirageRnd
-
-	thumb_func_start SetMirageRnd
-SetMirageRnd: @ 81378BC
-	push {r4,lr}
-	adds r4, r0, 0
-	ldr r0, =0x00004024
-	lsrs r1, r4, 16
-	bl VarSet
-	ldr r0, =0x00004025
-	lsls r4, 16
-	lsrs r4, 16
-	adds r1, r4, 0
-	bl VarSet
-	pop {r4}
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end SetMirageRnd
-
-	thumb_func_start InitMirageRnd
-InitMirageRnd: @ 81378E4
-	push {r4,lr}
-	bl Random
-	adds r4, r0, 0
-	bl Random
-	lsls r4, 16
-	lsls r0, 16
-	lsrs r0, 16
-	orrs r4, r0
-	adds r0, r4, 0
-	bl SetMirageRnd
-	pop {r4}
-	pop {r0}
-	bx r0
-	thumb_func_end InitMirageRnd
-
-	thumb_func_start UpdateMirageRnd
-UpdateMirageRnd: @ 8137904
-	push {r4,lr}
-	lsls r0, 16
-	lsrs r4, r0, 16
-	bl GetMirageRnd
-	adds r1, r0, 0
-	cmp r4, 0
-	beq _08137928
-	ldr r3, =0x41c64e6d
-	ldr r2, =0x00003039
-_08137918:
-	adds r0, r1, 0
-	muls r0, r3
-	adds r1, r0, r2
-	subs r0, r4, 0x1
-	lsls r0, 16
-	lsrs r4, r0, 16
-	cmp r4, 0
-	bne _08137918
-_08137928:
-	adds r0, r1, 0
-	bl SetMirageRnd
-	pop {r4}
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end UpdateMirageRnd
-
-	thumb_func_start IsMirageIslandPresent
-IsMirageIslandPresent: @ 813793C
-	push {r4-r6,lr}
-	bl GetMirageRnd
-	lsrs r6, r0, 16
-	movs r5, 0
-_08137946:
-	movs r0, 0x64
-	adds r1, r5, 0
-	muls r1, r0
-	ldr r0, =gPlayerParty
-	adds r4, r1, r0
-	adds r0, r4, 0
-	movs r1, 0xB
-	bl GetMonData
-	cmp r0, 0
-	beq _08137978
-	adds r0, r4, 0
-	movs r1, 0
-	bl GetMonData
-	ldr r1, =0x0000ffff
-	ands r1, r0
-	cmp r1, r6
-	bne _08137978
-	movs r0, 0x1
-	b _08137980
-	.pool
-_08137978:
-	adds r5, 0x1
-	cmp r5, 0x5
-	ble _08137946
-	movs r0, 0
-_08137980:
-	pop {r4-r6}
-	pop {r1}
-	bx r1
-	thumb_func_end IsMirageIslandPresent
-
-	thumb_func_start UpdateShoalTideFlag
-UpdateShoalTideFlag: @ 8137988
-	push {lr}
-	bl get_map_light_from_warp0
-	lsls r0, 24
-	lsrs r0, 24
-	bl is_light_level_1_2_3_5_or_6
-	lsls r0, 24
-	cmp r0, 0
-	beq _081379CE
-	bl RtcCalcLocalTime
-	ldr r1, =gUnknown_085B2B44
-	ldr r0, =gLocalTime
-	ldrb r0, [r0, 0x2]
-	lsls r0, 24
-	asrs r0, 24
-	adds r0, r1
-	ldrb r0, [r0]
-	cmp r0, 0
-	beq _081379C8
-	ldr r0, =0x0000089a
-	bl FlagSet
-	b _081379CE
-	.pool
-_081379C8:
-	ldr r0, =0x0000089a
-	bl FlagClear
-_081379CE:
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end UpdateShoalTideFlag
-
-	thumb_func_start Task_WaitWeather
-Task_WaitWeather: @ 81379D8
-	push {r4,lr}
-	lsls r0, 24
-	lsrs r4, r0, 24
-	bl sub_80AC3BC
-	lsls r0, 24
-	cmp r0, 0
-	beq _081379F2
-	bl EnableBothScriptContexts
-	adds r0, r4, 0
-	bl DestroyTask
-_081379F2:
-	pop {r4}
-	pop {r0}
-	bx r0
-	thumb_func_end Task_WaitWeather
-
-	thumb_func_start WaitWeather
-WaitWeather: @ 81379F8
-	push {lr}
-	ldr r0, =Task_WaitWeather
-	movs r1, 0x50
-	bl CreateTask
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end WaitWeather
-
-	thumb_func_start InitBirchState
-InitBirchState: @ 8137A0C
-	push {lr}
-	ldr r0, =0x00004049
-	bl GetVarPointer
-	movs r1, 0
-	strh r1, [r0]
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end InitBirchState
-
-	thumb_func_start UpdateBirchState
-UpdateBirchState: @ 8137A20
-	push {r4,r5,lr}
-	adds r4, r0, 0
-	lsls r4, 16
-	lsrs r4, 16
-	ldr r0, =0x00004049
-	bl GetVarPointer
-	adds r5, r0, 0
-	ldrh r0, [r5]
-	adds r4, r0
-	strh r4, [r5]
-	ldrh r0, [r5]
-	movs r1, 0x7
-	bl __umodsi3
-	strh r0, [r5]
-	pop {r4,r5}
-	pop {r0}
-	bx r0
-	.pool
-	thumb_func_end UpdateBirchState
diff --git a/data/time_events.s b/data/time_events.s
deleted file mode 100644
index 7a543fff58..0000000000
--- a/data/time_events.s
+++ /dev/null
@@ -1,7 +0,0 @@
-	.include "asm/macros.inc"
-	.include "constants/constants.inc"
-
-	.section .rodata
-
-gUnknown_085B2B44:: @ 85B2B44
-	.byte 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01
diff --git a/include/field_weather.h b/include/field_weather.h
index e12107e702..0bdebf747f 100644
--- a/include/field_weather.h
+++ b/include/field_weather.h
@@ -1,12 +1,175 @@
 #ifndef GUARD_WEATHER_H
 #define GUARD_WEATHER_H
 
-void fade_screen(u8, s8);
+#include "sprite.h"
 
+// Controls how the weather should be changing the screen palettes.
+enum {
+    WEATHER_PAL_STATE_CHANGING_WEATHER,
+    WEATHER_PAL_STATE_SCREEN_FADING_IN,
+    WEATHER_PAL_STATE_SCREEN_FADING_OUT,
+    WEATHER_PAL_STATE_IDLE,
+};
+
+struct Weather
+{
+    union
+    {
+        struct
+        {
+            struct Sprite *rainSprites[24];
+            struct Sprite *snowflakeSprites[101];
+            struct Sprite *cloudSprites[3];
+        } s1;
+        struct
+        {
+            u8 filler0[0xA0];
+            struct Sprite *fog1Sprites[20];
+            struct Sprite *ashSprites[20];
+            struct Sprite *fog2Sprites[20];
+            struct Sprite *sandstormSprites1[20];
+            struct Sprite *sandstormSprites2[5];
+        } s2;
+    } sprites;
+    u8 gammaShifts[19][32];
+    u8 altGammaShifts[19][32];
+    s8 gammaIndex;
+    s8 gammaTargetIndex;
+    u8 gammaStepDelay;
+    u8 gammaStepFrameCounter;
+    u16 fadeDestColor;
+    u8 palProcessingState;
+    u8 fadeScreenCounter;
+    bool8 readyForInit;
+    u8 taskId;
+    u8 unknown_6CA;
+    u8 unknown_6CB;
+    u16 initStep;
+    u16 finishStep;
+    u8 currWeather;
+    u8 nextWeather;
+    u8 weatherGfxLoaded;
+    bool8 weatherChangeComplete;
+    u8 weatherPicSpritePalIndex;
+    u8 altGammaSpritePalIndex;
+    u16 unknown_6D6;
+    u8 unknown_6D8;
+    u8 unknown_6D9;
+    u8 rainSpriteCount;
+    u8 unknown_6DB;
+    u8 unknown_6DC;
+    u8 rainStrength;
+    /*0x6DE*/ u8 cloudSpritesCreated;
+    u8 filler_6DF[1];
+    u16 unknown_6E0;
+    u16 unknown_6E2;
+    u8 snowflakeSpriteCount;
+    u8 unknown_6E5;
+    u16 unknown_6E6;
+    u16 thunderCounter;
+    u8 unknown_6EA;
+    u8 unknown_6EB;
+    u8 unknown_6EC;
+    u8 unknown_6ED;
+    u16 fog1ScrollPosX;
+    u16 unknown_6F0;
+    u16 unknown_6F2;
+    u8 lightenedFogSpritePals[6];
+    u8 lightenedFogSpritePalsCount;
+    u8 fog1SpritesCreated;
+    u16 unknown_6FC;
+    u16 unknown_6FE;
+    u8 ashSpritesCreated;
+    u8 filler_701[3];
+    u32 unknown_704;
+    u32 unknown_708;
+    u8 filler_70C[2];
+    u16 unknown_70E;
+    u16 unknown_710;
+    u16 unknown_712;
+    u16 unknown_714;
+    u8 sandstormSprites1Created;
+    u8 sandstormSprites2Created;
+    u16 unknown_718;
+    u16 unknown_71A;
+    u16 unknown_71C;
+    u16 unknown_71E;
+    u16 unknown_720;
+    u16 unknown_722;
+    u8 fog2SpritesCreated;
+    u8 filler_725[1];
+    u16 unknown_726;
+    u16 unknown_728;
+    u16 unknown_72A;
+    u16 unknown_72C;
+    u8 unknown_72E;
+    u8 filler_72F;
+    u16 currBlendEVA;
+    u16 currBlendEVB;
+    u16 targetBlendEVA;
+    u16 targetBlendEVB;
+    u8 blendUpdateCounter;
+    u8 blendFrameCounter;
+    u8 blendDelay;
+    u8 filler_73B[0x3C-0x3B];
+    s16 unknown_73C;
+    s16 unknown_73E;
+    s16 unknown_740;
+    s16 unknown_742;
+    u8 filler_744[0xD-4];
+    s8 loadDroughtPalsIndex;
+    u8 loadDroughtPalsOffset;
+};
+
+void StartWeather(void);
+void ChangeWeather(u8 weather);
+void sub_807C988(u8 effect);
+void sub_807C9B4(u8 effect);
+void Task_WeatherInit(u8);
+void Task_WeatherMain(u8);
+void sub_807CAE8(void);
+void nullsub_38(void);
+void SetWeatherScreenFadeOut(void);
+
+enum
+{
+    FADE_FROM_BLACK,
+    FADE_TO_BLACK,
+    FADE_FROM_WHITE,
+    FADE_TO_WHITE,
+};
+
+void FadeScreen(u8, u8);
+// ...
+void UpdateSpritePaletteWithWeather(u8 tag);
+void ApplyWeatherGammaShiftToPal(u8);
+// ...
+void Weather_SetBlendCoeffs(u8, u8);
+// ...
+void PlayRainSoundEffect(void);
+// ...
 void SetSav1Weather(u32);
 u8 GetSav1Weather(void);
-void sub_80AEDBC(void);
-
+void SetSav1WeatherFromCurrMapHeader(void);
+// ...
 void DoCurrentWeather(void);
+void sub_8080750();
+
+bool8 IsWeatherNotFadingIn(void);
+bool8 IsWeatherChangeComplete(void);
+void SetWeather(u32);
+void UpdateWeatherPerDay(u16);
+void PreservePaletteInWeather(u8 index);
+void ResetPreservedPalettesInWeather(void);
+extern void ResetDroughtWeatherPaletteLoading(void);
+void ResetDroughtWeatherPaletteLoading(void);
+bool8 LoadDroughtWeatherPalettes(void);
+u8 GetCurrentWeather(void);
+void LoadCustomWeatherSpritePalette(const u16 *palette);
+
+
+extern struct Weather gWeather;
+
+extern struct Weather *const gWeatherPtr;
 
 #endif // GUARD_WEATHER_H
diff --git a/include/overworld.h b/include/overworld.h
index 597a160edf..974f8f091d 100644
--- a/include/overworld.h
+++ b/include/overworld.h
@@ -70,6 +70,8 @@ void warp1_set_2(s8 mapGroup, s8 mapNum, s8 warpNum);
 void c2_load_new_map(void);
 void copy_saved_warp2_bank_and_enter_x_to_warp1(u8 unused);
 void mapldr_default(void);
+u8 get_map_light_from_warp0(void);
+bool8 is_light_level_1_2_3_5_or_6(u8 a1);
 
 void IncrementGameStat(u8);
 u32 GetGameStat(u8);
diff --git a/include/time_events.h b/include/time_events.h
new file mode 100644
index 0000000000..fd6d29f390
--- /dev/null
+++ b/include/time_events.h
@@ -0,0 +1,8 @@
+#ifndef GUARD_TIME_EVENTS_H
+#define GUARD_TIME_EVENTS_H
+
+void UpdateMirageRnd(u16);
+u8 IsMirageIslandPresent(void);
+void UpdateBirchState(u16);
+
+#endif // GUARD_TIME_EVENTS_H
diff --git a/ld_script.txt b/ld_script.txt
index f2a9d81963..d3bf4e845d 100644
--- a/ld_script.txt
+++ b/ld_script.txt
@@ -185,7 +185,7 @@ SECTIONS {
         src/pokeblock.o(.text);
         asm/fldeff_flash.o(.text);
         asm/post_battle_event_funcs.o(.text);
-        asm/time_events.o(.text);
+        src/time_events.o(.text);
         asm/birch_pc.o(.text);
         src/hof_pc.o(.text);
         asm/field_specials.o(.text);
@@ -472,7 +472,7 @@ SECTIONS {
         src/wallclock.o(.rodata);
         src/pokeblock.o(.rodata);
         data/fldeff_flash.o(.rodata);
-        data/time_events.o(.rodata);
+        src/time_events.o(.rodata);
         data/field_specials.o(.rodata);
         data/battle_records.o(.rodata);
         data/pokedex_area_screen.o(.rodata);
diff --git a/src/time_events.c b/src/time_events.c
new file mode 100644
index 0000000000..1f169a5c6c
--- /dev/null
+++ b/src/time_events.c
@@ -0,0 +1,118 @@
+#include "global.h"
+#include "time_events.h"
+#include "event_data.h"
+#include "field_weather.h"
+#include "pokemon.h"
+#include "random.h"
+#include "overworld.h"
+#include "rtc.h"
+#include "script.h"
+#include "task.h"
+
+static u32 GetMirageRnd(void)
+{
+    u32 hi = VarGet(VAR_MIRAGE_RND_H);
+    u32 lo = VarGet(VAR_MIRAGE_RND_L);
+    return (hi << 16) | lo;
+}
+
+static void SetMirageRnd(u32 rnd)
+{
+    VarSet(VAR_MIRAGE_RND_H, rnd >> 16);
+    VarSet(VAR_MIRAGE_RND_L, rnd);
+}
+
+// unused
+void InitMirageRnd(void)
+{
+    SetMirageRnd((Random() << 16) | Random());
+}
+
+void UpdateMirageRnd(u16 days)
+{
+    s32 rnd = GetMirageRnd();
+    while (days)
+    {
+        rnd = 1103515245 * rnd + 12345;
+        days--;
+    }
+    SetMirageRnd(rnd);
+}
+
+bool8 IsMirageIslandPresent(void)
+{
+    u16 rnd = GetMirageRnd() >> 16;
+    int i;
+
+    for (i = 0; i < PARTY_SIZE; i++)
+        if (GetMonData(&gPlayerParty[i], MON_DATA_SPECIES) && (GetMonData(&gPlayerParty[i], MON_DATA_PERSONALITY) & 0xFFFF) == rnd)
+            return TRUE;
+
+    return FALSE;
+}
+
+void UpdateShoalTideFlag(void)
+{
+    static const u8 tide[] =
+    {
+        1, // 00
+        1, // 01
+        1, // 02
+        0, // 03
+        0, // 04
+        0, // 05
+        0, // 06
+        0, // 07
+        0, // 08
+        1, // 09
+        1, // 10
+        1, // 11
+        1, // 12
+        1, // 13
+        1, // 14
+        0, // 15
+        0, // 16
+        0, // 17
+        0, // 18
+        0, // 19
+        0, // 20
+        1, // 21
+        1, // 22
+        1, // 23
+    };
+
+    if (is_light_level_1_2_3_5_or_6(get_map_light_from_warp0()))
+    {
+        RtcCalcLocalTime();
+        if (tide[gLocalTime.hours])
+            FlagSet(FLAG_SYS_SHOAL_TIDE);
+        else
+            FlagClear(FLAG_SYS_SHOAL_TIDE);
+    }
+}
+
+static void Task_WaitWeather(u8 taskId)
+{
+    if (IsWeatherChangeComplete())
+    {
+        EnableBothScriptContexts();
+        DestroyTask(taskId);
+    }
+}
+
+void WaitWeather(void)
+{
+    CreateTask(Task_WaitWeather, 80);
+}
+
+void InitBirchState(void)
+{
+    *GetVarPointer(VAR_BIRCH_STATE) = 0;
+}
+
+void UpdateBirchState(u16 days)
+{
+    u16 *state = GetVarPointer(VAR_BIRCH_STATE);
+    *state += days;
+    *state %= 7;
+}