WEATHER RULES

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WEATHER RULES - OVERVIEW

Weather in this system is an optional complexity tool for the Dungeon Master (DM). It represents shifting natural or supernatural conditions that can alter combat, travel, and survival.

When to Roll: At the start of each game session, before the party begins their preparation, the DM may choose to roll once on the D100 Weather Chart.

Player Notification: The DM should inform the players of the current weather before the adventure begins. This allows the party to adjust their gear, spells, or strategy to account for the conditions.

Optional Use: Weather is not required. It is an optional layer of immersion and difficulty. If the DM wants to add unpredictability, realism, or tactical challenges, they may include it. If not, play continues as normal.

Session Consistency: Once weather is rolled, it generally lasts the entire session unless the DM chooses to roll again mid-game (for example, when traveling multiple days or entering a region where conditions are unstable).

Modifiers in Play: The D100 Weather Chart provides clear mechanical effects on Ranged Attacks, Melee Attacks, Movement, Visibility, and Survival. Apply these modifiers immediately once the weather is revealed.

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SEASONAL WEATHER RULES

When rolling weather at the start of a session (or during long travel), the DM may choose to weight results based on the current season.

Method A — Direct Reroll: If the DM rolls a result that doesn’t fit the season (ex: blizzard in midsummer), they may reroll until a fitting result is found.

Method B — Weighted Shifts: Apply a +10 or -10 adjustment to the d100 roll depending on the season to skew results toward calmer or harsher weather.

Method C — Seasonal Subcharts: Use the same D100 chart, but apply the following guidelines to interpret results.

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SPRING (Thaw & Growth)

Frequent rain, storms, fog, and flooding.

Modify the Chart:

Results 1–20: Clear skies rare → reroll unless near coast or plains.

Results 30–60: Treat snow/blizzard results as rain or flooding.

Results 80+: Often thunderstorms or tornadoes instead of ice/snow events.

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SUMMER (Heat & Storms)

Heat waves, humidity, thunderstorms, drought, wildfires.

Modify the Chart:

Results 1–20: More sun, clear skies common.

Results 40–70: Replace snow/ice events with heat, humidity, or sandstorms.

Results 80+: More storms, hurricanes, and firestorms instead of blizzards.

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AUTUMN (Decay & Storm Season)

Storms, high winds, cold rains, early snow.

Modify the Chart:

Results 1–20: Clear but cooling air.

Results 30–60: Replace heavy heat results with steady rain, fog, or chill winds.

Results 70+: Storms are more likely than extreme heat or fire events.

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WINTER (Cold & Survival)

Snow, ice, blizzards, freezing winds.

Modify the Chart:

Results 1–20: Clear skies cold, but biting wind.

Results 30–70: Replace rain/flooding with snow, sleet, or ice.

Results 80+: Blizzards, whiteouts, frozen hurricanes dominate instead of heat-based disasters.

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DM Guidance

The D100 chart stays universal. The seasonal layer is just a lens for interpretation.

Example: A roll of 47 (Blizzard) in summer could instead be a monsoon storm or scorching drought. In winter, it remains a blizzard.

Seasonal adjustments should add realism but not slow play — the DM can decide quickly which version fits best.

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D100 WEATHER CHART WITH MODIFIERS

(Modifiers are cumulative penalties/bonuses. If blank, assume normal.)

Roll	Condition	Ranged Attacks (R)	Melee Attacks (M)	Movement (MV)	Visibility (VIS)	Survival (SURV)

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1–10: Clear / Mild

Roll	Condition	R	M	MV	VIS	SURV
1	Perfectly clear skies	–	–	–	Unlimited	–
2	Light clouds, sunny	–	–	–	Unlimited	–
3	Patchy clouds, pleasant breeze	–	–	–	Unlimited	–
4	Slight haze, warm air	–	–	–	Unlimited	–
5	Gentle wind	–	–	–	Unlimited	–
6	Cloud streaks, cooling air	–	–	–	Unlimited	–
7	Soft sunlight, calm	–	–	–	Unlimited	–
8	Lightly overcast	–	–	–	500 ft	–
9	Bright, warm with breeze	–	–	–	Unlimited	–
10	Clear evening skies	–	–	–	Unlimited	–

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11–25: Shifting Skies

Roll	Condition	R	M	MV	VIS	SURV
11	Thin overcast	–	–	–	400 ft	–
12	Warm humidity	–	–	-1	300 ft	Con checks after 8 hrs
13	Thickening clouds	–	–	–	350 ft	–
14	Gusts, mild	-1	–	–	300 ft	–
15	Distant thunder	–	–	–	250 ft	–
16	Patchy drizzle	-1	–	-1	250 ft	–
17	Cold front winds	-1	–	-1	250 ft	–
18	Light snowfall	-1	–	-1	200 ft	–
19	Intermittent drizzle	-1	–	–	200 ft	–
20	Winds shifting often	-1	–	–	200 ft	–
21	Mild fog	-2	–	–	100 ft	–
22	Low rolling clouds	–	–	–	200 ft	–
23	Light sleet	-1	–	-1	200 ft	–
24	Warm wind bursts	–	–	–	200 ft	–
25	Short shower	-1	–	-1	150 ft	–

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26–45: Moderate Weather

Roll	Condition	R	M	MV	VIS	SURV
26	Steady rain	-1	–	-1	100 ft	–
27	Cold drizzle	-1	–	-1	100 ft	–
28	Stronger wind	-2	–	-1	100 ft	–
29	Steady snow	-2	–	-2	80 ft	Con check/8 hrs
30	Fog bank	-3	–	-1	60 ft	–
31	Constant breeze	-1	–	–	120 ft	–
32	Gray overcast	–	–	–	150 ft	–
33	Mist near water	-2	–	–	80 ft	–
34	Heavy drizzle	-2	–	-1	100 ft	–
35	Howling winds	-2	–	-1	100 ft	–
36	Light hail	-2	-1	-1	80 ft	–
37	Hot dry wind	–	–	-1	120 ft	Water loss risk
38	Cold biting wind	–	-1	-1	120 ft	Frostbite risk
39	Pre-storm build	-1	–	–	80 ft	–
40	Rain + gusts	-2	–	-2	60 ft	–
41	Freezing sleet	-2	-1	-2	60 ft	Hypothermia risk
42	Heavy snow	-2	–	-2	50 ft	–
43	Sea swells	-2	–	-2 (sailing)	80 ft	Capsize risk
44	Dusty wind	-1	–	-1	80 ft	–
45	Wild temperature swings	-1	–	-1	100 ft	Con checks

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46–65: Harsh Weather

Roll	Condition	R	M	MV	VIS	SURV
46	Heavy rain	-2	-1	-1	60 ft	–
47	Blizzard	-3	-1	-2	30 ft	Con/1 hr
48	Dense fog	-3	–	-1	20 ft	–
49	Torrential downpour	-3	–	-2	40 ft	Flood risk
50	Lightning storm	-3	–	-2	40 ft	1/20 strike
51	Heavy hail	-3	-2	-2	40 ft	1 dmg/round exposed
52	Thunderclaps	-2	–	-1	40 ft	Morale checks
53	Gale winds	-4	-2	-2	30 ft	Flying impossible
54	Sandstorm	-3	-2	-3	10 ft	Suffocation check
55	Humidity oppressive	-2	–	-1	60 ft	Fatigue checks
56	Ice storm	-3	-2	-3	20 ft	Slip risk
57	Black skies	-2	–	-1	40 ft	Fear rolls
58	Snow piling	-2	–	-3	30 ft	–
59	Dust storm	-2	-1	-2	20 ft	Suffocation risk
60	Heatwave	–	-1	-2	60 ft	Con/hr
61	Fog + drizzle	-3	–	-2	30 ft	Nav impossible
62	Torn sails winds	-3	–	-2	40 ft	Sailing hazard
63	Flash flood risk	-2	–	-2	40 ft	Save vs drowning
64	Wild lightning	-3	–	-2	40 ft	1/10 strike
65	Freezing gale	-3	-2	-3	20 ft	Con/hr

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66–85: Deadly Weather

Roll	Condition	R	M	MV	VIS	SURV
66	Hurricane winds	-5	-3	-4	20 ft	Structures fail
67	Tornado nearby	-5	-5	Random	10 ft	Save vs death
68	Sheet ice	-3	-2	-4	30 ft	Fall risk
69	Acid rain	-3	-2	-2	30 ft	Gear corrodes
70	Red storm	-3	–	-2	30 ft	Magic misfires
71	Auroral anomaly	-2	–	-2	40 ft	Random magic
72	Earth tremors	-3	-2	-3	30 ft	Balance checks
73	Constant lightning	-3	–	-2	30 ft	1/5 strike
74	Sand tornadoes	-4	-3	-3	10 ft	Suffocation
75	Fist-sized hail	-4	-3	-3	20 ft	1d4 dmg/min
76	Whiteout blizzard	-4	-3	-4	5 ft	Con/30 min
77	Volcanic ash	-3	-2	-3	20 ft	Suffocate/poison
78	Cyclone	-5	-4	-4	20 ft	Save vs death
79	Ocean typhoon	-5	-3	-5	20 ft	Ship lost
80	Electrical storm	-3	-2	-3	30 ft	Spells surge
81	Extreme heat	-2	-2	-3	40 ft	Metal burns
82	Poison fog	-3	-2	-2	10 ft	Con/save
83	Frozen hurricane	-4	-3	-4	10 ft	Frostbite
84	Deafening thunder	-3	-2	-2	20 ft	Morale collapse
85	Rising floodwaters	-3	–	-4	20 ft	Drowning risk

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86–100: Apocalyptic

Roll	Condition	R	M	MV	VIS	SURV
86	Tornado touchdown	-5	-5	Random	10 ft	Save vs death
87	Hurricane-force winds	-5	-5	-5	5 ft	Buildings collapse
88	Firestorm	–	–	-5	20 ft	Burn 1d6/round
89	Volcanic eruption	-5	-5	-5	20 ft	Lava/ash
90	Multi-tornado supercell	-5	-5	Random	10 ft	Save vs death
91	Endless blizzard	-4	-4	-5	5 ft	Starvation risk
92	Black fog	-3	-3	-3	10 ft	Plants/animals die
93	Meteor shower	-5	-5	-5	40 ft	Impact dmg 2d10
94	Earthquake fissures	-5	-5	-5	30 ft	Save vs fall
95	Catastrophic flood	-5	–	Swimming only	30 ft	Drowning
96	Constant lightning	-5	–	-4	20 ft	Strike every rd
97	Ley-storm reality warp	-3	-3	-3	20 ft	Random chaos
98	Acid storm	-4	-3	-3	10 ft	Armor corrodes
99	Blood/ash storm	-4	-4	-4	10 ft	Fear & rot
100	World-ending event	-10	-10	-10	None	Death

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